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Prokaryote Genes Expression In Relation To Molecular Genetics

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Abstract

Energy economy is very important in all organisms as it ensures their survival. cell doesn’t have to waste energy, as it is energy consuming to produce all the enzymes needed to make an amino acid if that amino acid is available. Prokaryotes are always under attack of stress in the environment and don’t only require regulatory systems aimed to take full advantage of the gene expression throughout times of wealth but have also to sense danger emergency systems to remove threat or reduce damage. Economy is important, but backup plans guarantee species survives. The aim of this article is to review gene regulation in prokaryotes and the information flow also understand how it works and its importance finally using proteomics to understand functions on genome level gene regulation helps bacteria to adapt to environmental changes by changing gene expression thereby changing the proteins present in the cell.it is like a switch that can be turned on and off when needed. There are different ways of gene regulation which is mechanisms for determining the genes expressed and its level a lot of gene regulation occurs at the level of transcription. The area that regulate transcription is usually near the promoter region of a gene. Through regulating ability of RNA polymerase promoter binding. When RNA polymerase bind to initiate transcription of structural gene, cell can modulate the quantity of message produced thereby gene product quantity synthesized and regulatory sequences and regulatory proteins are the keys to regulate gene expression, operon system works as regulatory sequences in bacteria where genes related are found in sets also there are some examples of gene regulation systems as lac z operon and Tryptophan operon and housekeeping systems. Some regulatory sequenced work are inducible others are repressible. Viruses stop host cell gene expression as a mechanism of protection against host cell Antivirals there are some viruses’ mutants that can replicate without inhibiting gene expression which isn’t like the wild types where this process is called cytopathogenisity then after understanding Gene expression regulation and information flow through transcription and translation. Using proteomics help studding proteins expression and interaction although time and conditions of expression and gives good overview over structural and functional proteins which are used in Biotechnological applications as modifying enzymes as lipase and modifying specific biological catalysts that revolutionize industry and pharmaceuticals.

Introduction

prokaryotes are unicellular organisms with no nucleus or organelles. There are two different groups of prokaryotes which are bacteria and archaea. Prokaryote don’t have membrane-bound organelles. prokaryotes can undergo all cell reactions: the electron transport chain, ATP synthase, and photosynthesis. Their genetic material is located in a distinct area of the cell named the nucleoid. Prokaryotic chromosome is single covalently circular closed double stranded DNA molecule. some bacteria contain linear chromosomes and some prokaryotes contain more than one chromosome and circular small replicating components of DNA called plasmids. The cytoplasm is an aqueous jelly-like filling the cell and holds ribosomes which is protein-RNA complex that synthesize proteins. Prokaryotes contain cell walls a rigid structure surround plasma membrane helps offering protection and keeping cell shape1.

Prokaryotic Gene expression

Prokaryotes Genomic DNA is group of genetic orders that control all cell activities in prokaryotes and eukaryotes these instructions are translated through synthesis of RNA and proteins. The important role for presence for any organism is economy. A cell doesn’t have to waste energy, as it is energy consuming to produce all the enzymes needed to make an amino acid if that amino acid is available. Prokaryotes are always under attack of stress in the environment and don’t only require regulatory systems aimed to take full advantage of the gene expression throughout times of wealth but have also to sense danger emergency systems to remove threat or reduce damage. Economy is important, but backup plans guarantee species survival. 2 so gene regulation helps bacteria to adapt to environmental changes by changing gene expression thereby changing the proteins present in the cell3

Flow of information

Prokaryotic gene expression is regulated at two elementary levels: DNA transcription and mRNA translation. When produced protein isn’t needed anymore, transcription stops and transcription regulation is the first way to determine type and quantity of each expressed protein in a prokaryotic cell. The more protein is required, the more transcription happens in prokaryotic cells so the expression of genes controlled mostly at transcriptional level Also mRNA degradation, modification of protein activity, and protein degradation are important for gene expression regulation.3

How is gene expression regulated?

There are different ways of gene regulation which is mechanisms for determining the genes expressed and its level a lot of gene regulation occurs at the level of transcription.

Bacteria contain regulatory molecules that determine if a specific gene will be transcribed into mRNA or not. These molecules bind to DNA near the gene and inducing or stopping the transcription enzyme (RNA polymerase).4

The area that regulate transcription is usually near the promoter region of a gene. Through regulating ability of RNA polymerase promoter binding. When RNA polymerase bind to initiate transcription of structural gene, cell can modulate the quantity of message produced thereby gene product quantity synthesized. Lot of gene regulation occurs at the level of transcription. Genes in bacteria are found in groups on chromosome as they transcribed by same promoter where RNA polymerase bind. genes regulated through single promoter known as operon. Operons contain regulatory DNA sequences that control transcription of the operon. Operon regulatory sequences are binding sites for regulatory proteins, which determine quantity of operon transcribed. The promoter is an example of a regulatory DNA sequence. Regulatory proteins can stop transcription (negative control) or increase transcription (positive control). Regulatory proteins may need bound effector molecules as sugars or amino acids for action. Repressor proteins responsible for decreasing or stopping transcription and activator proteins are responsible for increasing transcription. Transcription initiation happens in three steps: RNA polymerase binding, isomerization of a few nucleotides, and escape of RNA polymerase from t promoter region that permits message elongation. Negative regulators block attachment while activators interrelate with RNA polymerase. [4 ,6]56. When operon under negative or positive control it is called inducible if another effector molecule is to increase expression of structural genes. And it can be repressible if effector molecule must attach to regulatory protein before stopping transcription of the structural genes.

Regulatory proteins can be induced or inhibited by specific molecules. The small molecule attaches to protein altering its configuration and change its ability to bind DNA. 7

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Operon systems examples

The lac operon

is an inducible operon. E. coli can use other sugars as energy sources when glucose is low. Lactose is one of these sugars. The lac operon regulates genes needed to process lactose from environment. The Z gene of the lac operon encodes beta-galactosidase that can cleave lactose to glucose and galactose. lac operon needs to be activated the glucose level have to be very low and there must be lactose. In glucose absence CAP protein attaching makes transcription of the more effective, it binds to the lac repressor and changes its configuration thus prevent transcription, It would be energetically wasteful to synthesize enzymes to cleave lactose if there were no lactose or glucose was present 6

Regulation of the lac operon. Transcription of the lac operon is carefully regulated so that its expression only occurs when glucose is limited and lactose is present to serve as an alternative fuel. It is activated when lactose is present (energy economy). The inducer is allolactose which is a form of lactose Other operons are activated and inhibited small molecule called a corepressor and operon is called repressible.

Tryptophan operon system

Escherichia coli needs amino acids, and can make many amino acids. E. coli can ingest from environment or synthesize using enzymes that are represented by five genes. These five genes are in cluster called tryptophan operon. The genes are transcribed one MRNA then produce five enzymes. If tryptophan is present, then E. coli does not make it and the trp operon is turned off. When tryptophan isn’t available, the operon is switched on and tryptophan is synthesized. When tryptophan increases, 2 trp molecules attach repressor protein at operator sequence so physically blocking the RNA polymerase from trancription.

Viruses affect host cell activities turning cell to work for its own functions which lead to cell changes known as cytopathic effects. Virus pathogenesis lead to inhibition of gene expression of host cell. Viral gene products can inhibit expression of host genes have been identified, as have some of the molecular targets of the host. virus-induced inhibition of gene expression is important for stopping antiviral response of host cell. Viruses stop gene expression of host that is crucial in viruses’ ability of pathogenesis(cytopathogenesis). Many virus families stop host genes expression when virus Genome is replicating. Because it makes high quantity of cell assets as nucleoside triphosphates enters in biosynthesis of gene products of virus. There viral mutants can’t stop host gene expression but can replicate. Virus-induced inhibition of RNA and protein synthesis leads to stopping interferon response of host cell. picornaviruses gene products stop host protein synthesis which doesn’t affect viral protein synthesis. Apoptosis(programmed cell death) is the host response to stop virus replication through death of virus infected cells. viruses can adapt apoptotic cells for example some influenza virus poorly replicate in cells produces anti apoptotic protein Bcl-2 than in control cells so stopping apoptosis increase virus replication time which results in higher virus yields.

Host transcription is inhibited by most RNA viruses. Influenza viruses are an exception because they replicate in host cell nucleus and needs the recently host transcripts made to make capped oligonucleotides which is utilizes as primers for viral mRNA making. RNA virus like picornaviruses and rhabdoviruses stop host RNA synthesis. virus proteins have been crucial for virus replication, poliovirus 3C protease and the VSV matrix (M) protein have secondary function in host gene expression stooping. Most proteins of viruses found in cytoplasm of infected cells where replication occurs The poliovirus 3C protease and VSV M protein are found in cytoplasm and nucleus of infected cells. where they play a role in replication and stopping gene expression of host. proteins of virus stop transcription using the host RNA polymerases. But in host RNAPII, the i4nhibition made through inactivation of transcription initiation factor, TFIID. TFIID is from seven initiation factors needed for transcription known as transcription general factors as they are needed forRNAPII-dependent genes, or as basal transcription factors. Promoters in case of absence of proteins attach to DNA sequence-specific enhancer components that enhance transcription of genes and regulate expression of genes. Due to its important job in transcription activation, TFIID is inactivated by viruses to stop expression of host genes viruses have mRNAs is translated in infected cells and host mRNAs translation is stopped. protein synthesis stopping is considered as antiviral activity while viral mRNAs translation happens because of adaptation of virus in the antiviral mechanisms. Thus, the first key issue in understanding the inhibition of host since viruses and hosts have same translational tool. viruses escape translation stopping by many ways: translation stopping and inhibition escape of virus, so that the relative importance of different mechanisms is usually also an issue. RNA viruses’ translation inhibition happens before stopping of host mRNA synthesizing. Translation inhibition in host cells is because of host translation factors.65

Proteomics of prokaryotes

proteomics field decide biochemical and cell activities and proteins structure on genome. Proteomics focus on protein‐protein interactions. Purified proteins biochemical analysis known functional proteomics. While Structural proteomics goal is to find the 3D structures of proteins. Structural proteomics only decide the experimental structures for some proteins and rest of structures is predicted computational methods.one of the problems facing Proteomics experimentally is that functional or structural proteomics is that many proteins are insoluble when expressed or purified then concentrated.9

Proteomics have started what is called post genomic era as it helps understanding genome sequences functions. Proteomes indicate functions of cells in different times and conditions. Proteomic analysis is complicated and needs methods to find position and function of proteins also their interaction with each other and measure Gene expression amount under different conditions and in different times.

Conclusion

Gene regulation is important for energy economy in cells as is it waste of energy to produced proteins or enzymes not needed by cells thus Gene regulation through regulatory sequences and proteins works as switch on and off in prokaryotes to determine genes to be turned on also in bacteria operon systems do this function as genes related are found in clusters and before prompter there is operon regulatory genes, there are inducible and repressible operons as lac z operon and tryptophan operon also there are housekeeping genes that works all time. Viruses pathogenicity inhibit gene expression to stop Antiviral host cell mechanism also there are some mutants that can replicate without disrupting gene expression, prokaryotes information flow is through transcription by RNA POLYMERASE and translation which happens simultaneously. Finally, proteomics the study of proteins on genome level and their expression rate and time helps studying prokaryotes phenology and modifying products used in biotechnology.

References

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  2. Battistuzzi, F. U., Feijao, A. & Hedges, S. B. A genomic timescale of prokaryote evolution: Insights into the origin of methanogenesis, phototrophy, and the colonization of land. BMC Evol. Biol. 4, (2004).
  3. Rosenberg, E., DeLong, E. F., Thompson, F., Lory, S. & Stackebrandt, E. The prokaryotes: Applied bacteriology and biotechnology. The Prokaryotes: Applied Bacteriology and Biotechnology vol. 9783642313318 (Springer-Verlag Berlin Heidelberg, 2013).
  4. Clark, M. A., Choi, J. & Douglas, M. Prokaryotic Gene Regulation. (2018).
  5. Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. & Reece, J. B. Campbell Biology + Masteringbiology With Etext Access Card Books a La Carte Edition. (Pearson College Div, 2016).
  6. Berg, J. M., Tymoczko, J. L. & Stryer, L. Prokaryotic DNA-Binding Proteins Bind Specifically to Regulatory Sites in Operons. (2002).
  7. Moat, A. G., Foster, J. W. & Spector, M. P. Microbial Physiology. Microbial Physiology (John Wiley & Sons, Inc., 2002). doi:10.1002/0471223867.
  8. Eisenberg, E. & Levanon, E. Y. Human housekeeping genes, revisited. Trends in Genetics vol. 29 569–574 (2013).
  9. Cristea, I. M., Gaskell, S. J. & Whetton, A. D. Proteomics techniques and their application to hematology. Blood vol. 103 3624–3634 (2004).
  10. Savchenko, A. et al. Strategies for structural proteomics of prokaryotes: Quantifying the advantages of studying orthologous proteins and of using both NMR and X-ray crystallography approaches. Proteins Struct. Funct. Bioinforma. 50, 392–399 (2003).

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Prokaryote Genes Expression In Relation To Molecular Genetics. (2022, February 17). Edubirdie. Retrieved August 16, 2022, from https://edubirdie.com/examples/prokaryote-genes-expression-in-relation-to-molecular-genetics/
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Prokaryote Genes Expression In Relation To Molecular Genetics. [online]. Available at: <https://edubirdie.com/examples/prokaryote-genes-expression-in-relation-to-molecular-genetics/> [Accessed 16 Aug. 2022].
Prokaryote Genes Expression In Relation To Molecular Genetics [Internet]. Edubirdie. 2022 Feb 17 [cited 2022 Aug 16]. Available from: https://edubirdie.com/examples/prokaryote-genes-expression-in-relation-to-molecular-genetics/
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