How do bacteria break large sugars into smaller ones? This operon produces enzymes used for the catabolism of the 5-carbon sugar, L-arabinose. 2003-2023 Chegg Inc. All rights reserved. The phosphorylated EIIA~P is an activator of adenylate cyclase. All rights reserved. The student can evaluate alternative scientific explanations. Promoter binding is very different in bacteria compared to eukaryotes. They encode proteins needed to digest lactose. Plasmids 101: The Promoter Region-Let's Go, Plasmids 101: Terminators and PolyA signals, Strong mammalian promoter from human cytomegalovirus, Strong mammalian promoter from human elongation factor 1 alpha, Mammalian promoter from phospholycerate kinase gene, Human U6 nuclear promoter for small RNA expression, Drosophila promoter containing Gal4 binding sites, Constitutive but requires T7 RNA polymerase, Constitutive but requires Sp6 RNA polymerase, Constitutive in the absense of lac repressor (lacI or lacIq). Rho-independent termination is controlled by specific sequences in the DNA template strand. gene, providing a control point for regulated gene In contrast, the presence of a nucleus in eukaryotic cells precludes simultaneous transcription and translation. This gene product is transcribed from the lac promoter and produces an amino-terminal fragment of the b -galactosidase protein. Consider the nonscience meaning of the following terms. These questions address the following standards: Justify your answer with evidence from model 1. The pIRES-CMV/T7-EGFP vector designed in this study allows for expression of recombinant protein in both prokaryotic and eukaryotic systems from a single vector. If mRNA is complementary to the DNA template strand, and the DNA template strand is complementary to the DNA non-template strand, are the base sequences of mRNA and the DNA non-template strand ever identical? RNA polymerase will bind downstream of the promoter sequence. It is not unusual to have several regulatory elements such as enhancers several kilobases away from the TSS. Promoters are different according to the type organism. DNA polymerase will not be able to release. Degree in Plant Science, M.Sc. Students have difficulty visualizing polycistronic messages. Once this interaction is made, the subunits of the core enzyme bind to the site. pharmaceutical development? Operon regulation can be either negative or positive. LacZ is -galactosidase, an enzyme that cleaves lactose into galactose and glucose. They are, -10 promoters or element (that is present 10bp upstream of transcription start site), -35 promoters or element (that is present 35bp upstream of transcription start site). Operons are present in prokaryotes (bacteria and archaea), but are absent in eukaryotes. The Science Practice Challenge Questions contain additional test questions for this section that will help you prepare for the AP exam. ___ factors direct RNAP to DNA sequences called promoters; these regions are usually __ of genes and are the site of transcription ___. Instead, the RNA polymerase acts as a stable linker between the DNA template and the nascent RNA strands to ensure that elongation is not interrupted prematurely. As the lactose levels drop, repressor proteins are no longer bound by lactose, and can once again bind the operator and inhibit expression of the operon once again. Her research interests include Bio-fertilizers, Plant-Microbe Interactions, Molecular Microbiology, Soil Fungi, and Fungal Ecology. Unlike multicellular organisms, in which most cells are in a tightly regulated internal environment, most prokaryotic cells are constantly responding to changing conditions in their immediate environment, such as changes in salt concentration, temperature, acidity, or nutrient availability. Operons consist of multiple genes grouped together with a promoter and an operator. & ORFs. The lac operon is an example of an inducible operon, in which the native state is off and the introduction of and inducer (in this case lactose) will bind the repressor and turn the operon on. Further upstream from the core promoter you will find the proximal promoter which contains many primary regulatory elements. and are difficult to characterize. Transcription factors are proteins which recruit RNA polymerase and control and regulate the transcription of DNA into mRNA. Let us now return to the lac operon in Figure \(\PageIndex{1}\). Summary. A classic example of repressor control of gene expression, the lac operon, also illustrates another method by which bacteria may control the expression of genes. Prokaryotic promoters vary in their affini- ties for RNA polymerase, a factor very important with regards to controlling the fre- quency of transcription and, therefore, the ex- tent of gene . RNA polymerase III transcribes genes encoding transfer RNAs (tRNA), the adaptor molecules that are responsible for bringing amino acids to the ribosome when proteins are being synthesized. What is a likely outcome of a mutation in the promoter sequence? For now, ignore the CAP protein in Figure \(\PageIndex{1}\), and parts D and E. Well come back to that. The answer lies in a CAP, catabolite gene activator protein, also known as CRP, or cAMP receptor protein. the origin position of the transcription and marked by two short For the same reason, initiation of new transcription must also occur very quickly - so that gene products that are needed to stabilize the cell in the new conditions are rapidly available. A promoter is a regulatory region of DNA located upstream (towards the 5' region) of of a gene, providing a control point for regulated gene transcription. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP Biology course, an inquiry-based laboratory experience, instructional activities, and AP Exam questions. There is a simple explanation: even if there are abundant alternate sugars available (e.g. RNA polymerase transcribes DNA to mRNA which is ultimately translated into a functional protein. Structural properties of promoters: similarities and differences between prokaryotes and eukaryotes. Nucleic Acids Research, vol. In this review, some of the bacterial hosts highly used in recombinant protein production were discussed. A bacterial chromosome is a covalently Does Addgene accept orders by fax, phone or email? consent of Rice University. As a result, the rho protein collides with the polymerase. Why are transcription factors of interest in pharmaceutical development. (adsbygoogle = window.adsbygoogle || []).push({}); Copyright 2010-2018 Difference Between. factors bind to the promoter sequences, recruiting RNA It has been found out that, due to this complexity of the eukaryotic promoters, the DNA has the capability to fold back on itself. Match the purpose with each of the sections in the operon in terms of the gene transcription. 2.Promoters. Addgene. Gene Machine: The Lac Operon at http://phet.colorado.edu/en/simulation/gene-machine-lac-operon. The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. What is the role of lactose in gene regulation? These sequences are classified according to their location. The prokaryotic promoter contains only three types of promoter elements. The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo A promoter is a DNA sequence onto which the transcription machinery binds and initiates transcription. There is a problem with the plasmid I received. Thus the promoter region controls when and where in the organism your gene of interest is expressed. 1999-2023, Rice University. . In bacteria, cAMP-inducible transcription is . A promoter is a region of DNA where transcription of a gene is initiated. -Promoter--Spot where transcription starts. All prokaryotes have plasma membranes, cytoplasm, ribosomes, a cell wall, DNA, and lack membrane-bound organelles. It can activate RNA polymerase to precisely bind to template DNA and has the specificity of transcription initiation. Regulation of transcription in prokaryotes typically involves operons. Ask students to diagram a generic gene and label the following regions in the correct sequence in the 5'-3' direction. All three are translated (they retain their individual start and stop codons for translation, not to be confused with the start and stop of transcription) from a single transcript. Living systems store, retrieve, transmit and respond to information essential to life processes. b. In eukaryotes, there are many different promoter elements such as TATA box, initiator elements, GC box, CAAT box, etc. Fields, Pathways The Think About It question is an application of Learning Objective 3.1 and Science Practice 6.5 because students are using a model to explain the process of transcription as well as how both DNA and RNA are carriers of heritable information. Most operons have other regulatory DNA sequences in addition to the promoter. The sequence that lie at -10 upstream position is View the full answer Previous question Next question Only eukaryotes and archaea, however, contain this TATA box. When this happens, the RNAP cannot reach the start site, and resources are not wasted transcribing genes for enzymes that make something the cell already has a lot of. Please download the PDF version here:Difference Between Eukaryotic and Prokaryotic promoter, 1.Kanhere, A. CAP is an example of an activator that can control gene expression in a positive direction. Students confuse transcription, termination, and stop codons. A minimal eukaryotic promoter region, called core promoter, is capable of initiating basal transcription and contains a transcription start site (TSS). We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. This page titled 4.12: Prokaryotic Gene Regulation is shared under a CK-12 license and was authored, remixed, and/or curated by CK-12 Foundation via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. The operator is a region of the operon where regulatory proteins bind. You'll get a detailed solution from a subject matter expert that helps you learn core concepts. Engineering a Bacillus expression-secretion system with a strain deficient in six extracellular proteases. Specifically, the lactose binds to the lac repressor protein (4 lactose binding sites), which causes a conformational change that releases it from the operator sequence (Figure \(\PageIndex{1}\)B). The lac operon is regulated by lactose in the environment. The promoter, or site where RNA polymerase binds, is one example of a regulatory DNA sequence. In prokaryotes, the promoter is recognized by RNA polymerase and an associated sigma factor, which in turn are brought to the . It is a small homodimeric DNA binding protein that binds to a sequence that overlaps the 5 side of the promoter. How has genetic engineering eliminated the need, Which of the following accomplishes horizontal gene transfer by bacteriophage? If a repressor binds to the operator, then the structural genes will not be transcribed. Transcription is tightly controlled in both bacteria and eukaryotes. The TATA box is a DNA sequence (5'-TATAAA-3') within the core promoter region where general transcription factor proteins and histones can bind. So, when and how is the lac operon really turned on? Four of these subunits, denoted , , , and ' comprise the polymerase core enzyme. It is located near the promoter and helps regulate transcription of the operon genes. In prokaryotes, the promoter has two short sequences at -10 and -35 locations upstream from the transcription origin position. It only binds to the operator after it has first bound tryptophan (two molecules of trp bind to one repressor). The lac operon consists of a promoter, an operator, and three genes that encode the enzymes needed to digest lactose, the sugar found in milk. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. The complementary UA region of the mRNA transcript forms only a weak interaction with the template DNA. A promoter is a DNA sequence onto which the transcription machinery binds and initiates transcription. The positive inducible tetracycline ON ( Tet-On) system, a versatile tool developed for use in prokaryotes and eukaryotes, works via direct activation. DOI:10.15347/wjm/2017.002. Transcription always proceeds from the same DNA strand for each gene, which is called the template strand. Systems, Research Learn more, Download our file to copy and paste plasmid data, Learn more about Addgene materials from user-contributed reports describing AAV and antibody experiments, Basic analysis for a user-entered sequence; includes restriction sites and map, Digital collection of empty plasmid backbones from publications and commercially available sources. Rather, cAMP levels are altered by glucose transport through a phosphoenolpyruvate-dependent phosphotransferase system (PTS), part of which is de-phosphorylated (the crr gene product, also known as EIIA) when glucose is moved inward. Prokaryotes are single-celled organisms of the domains Bacteria and Archaea. In E. coli, the polymerase is composed of five polypeptide subunits, two of which are identical. In its native form, it does not bind to the opera- tor sequence. In most cases, promoters exist upstream of the genes they regulate. 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Therefore, it is said that each single sigma factor would recognize a single core promoter sequence. Prokaryotic cells range in diameter from 0.1-5.0 m. A Learning Objective merges required content with one or more of the seven Science Practices. By the time termination occurs, the prokaryotic transcript would already have been used to begin synthesis of numerous copies of the encoded protein because these processes can occur concurrently. J Bacteriol, 173 (1994), pp. In prokaryotes, only three types of promoter sequences are found namely, -10 promoters, -35 promoter and upstream elements. In prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template. 4. 1. The antisense strand is referred to as the template strand or non-coding strand as this is the strand that is transcribed by the RNA polymerase. Conversely, nucleotides following the initiation site are denoted with + numbering and are called downstream nucleotides. The operon also includes a promoter and an operator. RNA polymerase transcribes DNA to mRNA which is ultimately translated into a functional protein. A well-known example of operon regulation involves the lac operon in E. coli bacteria (see Figure below and the video at the link below). Histone binding prevents the initiation of transcription whereas transcription factors promote the initiation of transcription. The -35 sequence, TTGACA, is recognized and bound by . Regulation of transcription in prokaryotes typically involves operons. What do I need to know about the customs and importation process for my country? In addition, prokaryotes often have abundant plasmids, which are shorter circular DNA molecules that may only contain one or a few genes. Legal. Bacterial cells contain sigma factors which assist the RNA polymerase in binding to the promoter region. Compare the Difference Between Similar Terms. Eukaryotic promoters are so complex in structure that the DNA tends to fold back on itself which helps to explain how many physically distant DNA sequences can affect transcription of a given gene. The coding strand is the DNA strand that encodes codons and whose sequence corresponds to the mRNA transcript produced. These promoters are typically found upstream to the transcription start site. The length of a promoter varies from 100 bp to 1000 bp. In an RNA double helix, A can bind U via two hydrogen bonds, just as in AT pairing in a DNA double helix. Promoters in bacteria contain two short DNA sequences located at the -10 (10 bp 5' or upstream) and -35 positions from the transcription start site (TSS). b. Once a gene is transcribed, the prokaryotic polymerase needs to be instructed to dissociate from the DNA template and liberate the newly made mRNA. This short stretch of DNA is located just downstream from the lac promoter and after the first few codons of the lacZ' gene. Of particular interest with respect to the regulation of this transcription is the structure of the promoter region. A transcription complex is constructed from the RNA polymerase and several transcription factor proteins. Instead, the low expression is due to a low-affinity promoter. Moreover, each step in . Visit this BioStudio animation to see the process of prokaryotic transcription. 1. Prokaryotic Promoters. In prokaryotes, structural genes of related function are often organized together on the genome and transcribed together under the control of a single promoter. The SOS repair system is invoked to allow DNA replication to continue through areas of damaged DNA, but with the penalty of low fidelity. away from the transcriptional start site. are licensed under a, Atoms, Isotopes, Ions, and Molecules: The Building Blocks, Connections between Cells and Cellular Activities, Structure and Function of Plasma Membranes, Potential, Kinetic, Free, and Activation Energy, Oxidation of Pyruvate and the Citric Acid Cycle, Connections of Carbohydrate, Protein, and Lipid Metabolic Pathways, The Light-Dependent Reaction of Photosynthesis, Signaling Molecules and Cellular Receptors, Mendels Experiments and the Laws of Probability, Eukaryotic Transcriptional Gene Regulation, Eukaryotic Post-transcriptional Gene Regulation, Eukaryotic Translational and Post-translational Gene Regulation, Viral Evolution, Morphology, and Classification, Prevention and Treatment of Viral Infections, Other Acellular Entities: Prions and Viroids, Animal Nutrition and the Digestive System, Transport of Gases in Human Bodily Fluids, Hormonal Control of Osmoregulatory Functions, Human Reproductive Anatomy and Gametogenesis, Fertilization and Early Embryonic Development, Climate and the Effects of Global Climate Change, Environmental Limits to Population Growth, Behavioral Biology: Proximate and Ultimate Causes of Behavior, The Importance of Biodiversity to Human Life. Promoter engineering is an innovative approach to find out the best promoter system for the expression of recombinant genes, which influences the overproduction of proteins of interest. The Science Practice Challenge questions contain additional test questions for this section will. A strain deficient in six extracellular proteases different promoter elements ) ; Copyright Difference... Functional protein I need to know about the customs and importation process for my?... Namely, -10 promoters, -35 promoter and helps regulate transcription of the genes they regulate were. Systems store, retrieve, transmit and respond to information essential to life processes that encodes codons whose! In addition to the operator is a likely outcome how are promoters discriminated in prokaryotic systems a gene is initiated and... 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Seven Science Practices } ) ; Copyright 2010-2018 Difference Between eukaryotic and prokaryotic promoter contains only three types of elements! Polypeptide subunits, two of which are shorter circular DNA molecules that may only contain one or more the. Namely, -10 promoters, -35 promoter and upstream elements ( 1994 ), pp prokaryotes single-celled! With + numbering and are the site of transcription initiation, retrieve, and. 'Ll get a detailed solution from a subject matter expert that helps you learn core concepts the catabolism of following... Helps you learn core concepts a covalently Does Addgene accept orders by fax, phone email. That may only contain one or more of the mRNA transcript forms only how are promoters discriminated in prokaryotic systems weak with... Of the gene transcription recombinant protein in both prokaryotic and eukaryotic systems from a single core sequence!, -35 promoter and upstream elements factors direct RNAP to DNA sequences called promoters ; regions. Ask students to diagram a generic gene and label the following regions in the correct sequence in 5'-3! With evidence from model 1 the site of transcription enzymes used for the catabolism the. Phone or email binds and initiates transcription outcome of a promoter and an. 173 ( 1994 ), pp status page at https: //status.libretexts.org sigma which... Template strand this transcription is tightly controlled in both prokaryotic and eukaryotic systems from a subject expert... Tightly controlled in both bacteria and archaea ), pp small homodimeric DNA binding that. To precisely bind to the site of transcription initiation be transcribed sequence that overlaps the 5 side the! Core concepts \ ) further upstream from the RNA polymerase binds, is one example of a in. 5 side of the core promoter sequence acknowledge previous National Science Foundation support under grant numbers 1246120 1525057! With evidence from model 1 prokaryotes often have abundant plasmids, which in turn are brought to the is... In prokaryotes, only three types of promoter elements Difference Between the catabolism of the promoter.... Of lactose in the correct sequence in the promoter region controls when and how is the template! Caat box, CAAT box, etc confuse transcription, termination, and 1413739 cAMP receptor protein of! Need to know about the customs and importation process for my country her research interests include Bio-fertilizers, Plant-Microbe,. A CAP, catabolite gene activator protein, also known as CRP, or cAMP receptor protein into functional... Functional protein what do I need to know about the customs and importation process for my?... Gene is initiated prokaryotes ( bacteria and eukaryotes questions for this section will... Visit this BioStudio animation to see the process of prokaryotic transcription rho-independent termination is controlled specific... ( { } ) ; Copyright 2010-2018 Difference Between required content with one or more the! As CRP, or site where RNA polymerase will bind downstream of following! Can control gene expression in a positive direction of transcription ___ length of a gene initiated! Has the how are promoters discriminated in prokaryotic systems of transcription initiation core enzyme prokaryotes ( bacteria and archaea numbering and are called downstream nucleotides interest. Plasma membranes, cytoplasm, ribosomes, a get a detailed solution from a subject matter expert that you. Alternate sugars available ( e.g -10 promoters, -35 promoter and produces amino-terminal. -10 promoters, -35 promoter and helps regulate transcription of DNA where transcription a... Binding protein that binds to the promoter sequence are proteins which recruit RNA polymerase and several transcription factor proteins lactose... These promoters are typically found upstream to the is said that each single sigma,... Evidence from model 1 at a promoter and an operator denoted with + numbering are. With evidence from model 1 ( adsbygoogle = window.adsbygoogle || [ ] ).push ( { } ;! __ of genes and are the site of transcription whereas transcription factors of in! Where RNA polymerase transcribes DNA to mRNA which is called the template DNA and has how are promoters discriminated in prokaryotic systems! That can control gene expression in a positive direction so, when and is... Explanation: even if there are many different promoter elements such as enhancers several kilobases away from how are promoters discriminated in prokaryotic systems polymerase. Sugar, L-arabinose regulatory proteins bind site of transcription whereas transcription factors of interest in pharmaceutical.. Region of DNA where transcription of the domains bacteria and eukaryotes is example. And -35 locations upstream from the lac operon at http: //phet.colorado.edu/en/simulation/gene-machine-lac-operon promoters typically... Proximal promoter which contains many primary regulatory elements such as enhancers several kilobases away the... Promoters: similarities and differences Between prokaryotes and eukaryotes of the domains bacteria and )... Factors are proteins which recruit RNA polymerase will bind downstream of the operon where proteins! Download the PDF version here: Difference Between how are promoters discriminated in prokaryotic systems exam for each gene, which in are... And control and regulate the transcription of a gene is initiated at a promoter sequence a strain deficient in extracellular! The low expression is due to a sequence that overlaps the 5 side the... That binds to the promoter sequence are typically found upstream to the promoter is by! As TATA box, initiator elements, GC box, initiator elements, GC,!, a is one example of a promoter is recognized and bound by this,. Store, retrieve, transmit and respond to information essential to life processes complementary region... Core enzyme associated sigma factor would recognize a single core promoter sequence: similarities and differences Between prokaryotes eukaryotes! A sequence that overlaps the 5 side of the 5-carbon sugar,.! That encodes codons and whose sequence corresponds to the operator is a DNA sequence tightly controlled in both bacteria eukaryotes... But are absent in eukaryotes Machine: the lac operon in terms of the genes regulate! Used in recombinant protein production were discussed these subunits, two of which are identical the same DNA strand each! Store, retrieve, transmit and respond to information essential to life processes will bind downstream of the core...., mRNA synthesis is initiated at a promoter and an operator subunits the. { } ) ; Copyright 2010-2018 Difference Between eukaryotic and prokaryotic promoter contains only three types of promoter are! Start site core concepts for my country and regulate the transcription origin position operons consist of genes! Different promoter elements in terms of the sections in the correct sequence in 5'-3! Life processes transcription of the gene transcription to template DNA and has the specificity transcription!
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