User:Jordan Scott/Sandbox RNA polII: Difference between revisions
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[[ Image:Label RNA pol II (1).png|150px|right|thumb| RNAP II transcription process.]] | [[ Image:Label RNA pol II (1).png|150px|right|thumb| RNAP II transcription process.]] | ||
RNA Polymerases (RNAPs) are a group of enzymes that synthesize RNA in a process called transcription. During transcription the polymerase reads the DNA template strand and produces a RNA strand complementary to the template strand. The nascent RNA matches the DNA coding strand. Transcription can be divided into three processes that are discussed below: initiation, elongation and termination. Transcription in eukaryotes requires more distinct proteins for effective control. We see this as prokaryotic organisms have one core polymerase that synthesizes all of their RNA. However, eukaryotes have three distinct RNAPs named RNAP I, II, and III. RNAP I synthesizes rRNA precursors and RNAP III makes tRNA and the 5s rRNA. (A) | RNA Polymerases (RNAPs) are a group of enzymes that synthesize RNA in a process called transcription. During transcription the polymerase reads the DNA template strand and produces a RNA strand complementary to the template strand. The nascent RNA matches the DNA coding strand. Transcription can be divided into three processes that are discussed below: initiation, elongation and termination. Transcription in eukaryotes requires more distinct proteins for effective control. We see this as prokaryotic organisms have one core polymerase that synthesizes all of their RNA. However, eukaryotes have three distinct RNAPs named RNAP I, II, and III. RNAP I synthesizes rRNA precursors and RNAP III makes tRNA and the 5s rRNA. <ref>PMID: 1883205</ref>(A) | ||
RNAP II is responsible for the synthesis of pre-mRNA and snRNAs. It is 550 kDa and made of 12 subunits (Rpb1-12) that range from 220-10 kDa. The subunits are highly conserved to the point that mammalian subunits can substitute with yeast subunits are there are little to no defects.(B0) There are two large sub units and 10 smaller subunits, some of which are shared with RNAPs I and III. The active site of RNAP II is mostly made of the the two largest subunits Rpb1 and Rpb2. Rpb1 also has a CTD that contains heptad repeats of YSPTSPS.(G) This region serves as the main control point for RNAP II. The CTD experiences various conformation changes based on it being in a hypo or hyper phosphorylation state. The heptad repeats may also exist in several forms with one repeat having 16 known states. These states form a CTD code that is used to regulate the various stages of transcription and mRNA processing. The CTD is also shown to a part of cell cycle regulation as CDK/cyclins involved in the cell cycle modify the CTD and coordinate gene expression. (G) While RNAP II is capable of transcription by itself it is non-selective of any particular DNA region. However some mutageneis studies have shown that RNAP II may have some role in selectivity. (A) To properly recognize regions upstream of the gene's transcription start site it requires several general transcription factors that are selective for these regions known as promoters and positions RNAP to accurately begin transcription. (B) These GTF's and other accessory proteins called SRBs are necessary for accurate transcription and together with the RNAP II core enzyme form the RNAP holoenzyme. | RNAP II is responsible for the synthesis of pre-mRNA and snRNAs. It is 550 kDa and made of 12 subunits (Rpb1-12) that range from 220-10 kDa. The subunits are highly conserved to the point that mammalian subunits can substitute with yeast subunits are there are little to no defects.(B0) There are two large sub units and 10 smaller subunits, some of which are shared with RNAPs I and III. The active site of RNAP II is mostly made of the the two largest subunits Rpb1 and Rpb2. Rpb1 also has a CTD that contains heptad repeats of YSPTSPS.(G) This region serves as the main control point for RNAP II. The CTD experiences various conformation changes based on it being in a hypo or hyper phosphorylation state. The heptad repeats may also exist in several forms with one repeat having 16 known states. These states form a CTD code that is used to regulate the various stages of transcription and mRNA processing. The CTD is also shown to a part of cell cycle regulation as CDK/cyclins involved in the cell cycle modify the CTD and coordinate gene expression. (G) While RNAP II is capable of transcription by itself it is non-selective of any particular DNA region. However some mutageneis studies have shown that RNAP II may have some role in selectivity. (A) To properly recognize regions upstream of the gene's transcription start site it requires several general transcription factors that are selective for these regions known as promoters and positions RNAP to accurately begin transcription. (B) These GTF's and other accessory proteins called SRBs are necessary for accurate transcription and together with the RNAP II core enzyme form the RNAP holoenzyme. | ||
