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> > >Unit 4: > > >Post Transcriptional Modifications, Processing of Eukaryotic RNA and
Gene Regulation > > >
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>Transcription regulation in prokaryotes >
>Transcription regulation in prokaryotes refers to the process by which gene
expression is controlled at the level of transcription through the binding
of regulatory proteins to specific DNA sequences, allowing cells to adapt to
changes in their environment by altering gene expression. >
Explanation
>Transcription regulation in prokaryotes refers to the process by which gene
expression is controlled at the level of transcription, which is the first
step in the process of gene expression. In prokaryotes, transcription is
regulated primarily by the binding of regulatory proteins to specific DNA
sequences, called regulatory elements or promoter regions, located near the
start site of a gene. >
>Prokaryotic transcriptional regulation is often mediated by two types of
proteins: transcription factors and sigma factors. Transcription factors are
proteins that bind to regulatory elements and either activate or repress
transcription. Sigma factors are proteins that bind to RNA polymerase, the
enzyme responsible for transcribing DNA into RNA, and direct it to specific
promoter regions. >
>In addition to transcription factors and sigma factors, prokaryotic
transcriptional regulation can also involve small molecules such as inducers
and repressors, which bind to regulatory proteins and modulate their
activity. >
>Overall, transcription regulation in prokaryotes is a complex process that
allows cells to respond to changes in their environment and adapt to new
conditions by altering gene expression. >
>Steps included >
>Transcription regulation in prokaryotes involves several steps,
including: >
>Recognition of promoter: Transcription begins with the recognition of the
promoter region by the RNA polymerase enzyme, which binds to the DNA at
the promoter region of the gene to be transcribed. >
>Binding of regulatory proteins: Regulatory proteins, such as
transcription factors and sigma factors, bind to specific DNA sequences
near the promoter region and modulate the activity of RNA polymerase. This
can either activate or repress transcription. >
>Initiation of transcription: Once the RNA polymerase is bound to the
promoter and regulatory proteins are present, the initiation of
transcription begins. RNA polymerase begins to synthesize a complementary
RNA strand using the DNA template strand as a guide. >
>Elongation of RNA transcript: During the elongation phase, the RNA
polymerase continues to move along the DNA strand, synthesizing a
complementary RNA transcript. >
>Termination of transcription: Once the RNA polymerase reaches the end of
the gene, it reaches a termination sequence that signals the end of
transcription. The newly synthesized RNA transcript is released from the
DNA template. >
>Overall, transcription regulation in prokaryotes is a complex process that
involves the interplay of several regulatory proteins, RNA polymerase, and
DNA sequences to control gene expression. >
>Transcription regulation in eukaryotes >
>Transcription regulation in eukaryotes is a complex process that involves
several layers of regulation to control gene expression. Unlike prokaryotes,
eukaryotes have a more complex genome organization and transcriptional
regulation involves multiple mechanisms, including chromatin remodeling, DNA
methylation, and post-transcriptional regulation. >
>One of the key differences in transcription regulation between prokaryotes
and eukaryotes is the presence of a nucleus in eukaryotic cells, which
separates the DNA from the cytoplasmic environment. This necessitates the
involvement of additional regulatory proteins and processes to regulate
transcription. >
>In eukaryotes, transcriptional regulation involves the interaction of
transcription factors with specific regulatory sequences, called enhancers
and silencers, located far away from the gene's promoter region. These
enhancers and silencers can be located within the same gene or even on a
different chromosome. >
>Another layer of regulation involves the modification of chromatin
structure through histone modification and DNA methylation, which can either
promote or inhibit transcription by making the DNA more or less accessible
to transcription factors and RNA polymerase. >
>Finally, post-transcriptional regulation, such as alternative splicing, RNA
editing, and mRNA degradation, also plays a critical role in controlling
gene expression in eukaryotes. >
>In conclusion, transcription regulation in eukaryotes is a complex and
highly regulated process that involves multiple layers of regulation to
control gene expression in a cell-specific and developmentally regulated
manner. >