Updating the rna polymerase ctd code
Salient findings were that: (i) Tyr1, Pro3, Ser5, and Pro6 are essential for viability, by the criterion that Ala substitution is lethal, whereas Ser2, Thr4, and Ser7 are not; (ii) Phe is functional in lieu of Tyr1.
We also made double-mutants that subtracted two phosphoacceptors in each heptad and found that – Elucidating a core CTD vocabulary necessitates answering two key questions: (i) how are essential coding letters organized into readable words?
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Dynamic phosphorylation of Ser2, Ser5 and Ser7 residues orchestrates the binding of transcription and RNA processing factors to the transcription machinery.
Gppp N cap is a signature feature of eukaryal m RNA that is required for m RNA stability and efficient translation.
Cap synthesis entails three enzymatic reactions: (i) the 5’ triphosphate end of the pre-m RNA is hydrolyzed to a diphosphate by RNA triphosphatase; (ii) the diphosphate RNA end is capped with GMP by RNA guanylyltransferase; and (iii) the Gppp N cap is methylated by RNA (guanine-N7) methyltransferase.
Translating this “thought experiment” into action, we sought to override the requirement for Ser5, and Ser5 phosphorylation, by fusing an essential cellular Ser5-PO receptor – the m RNA capping enzymes RNA triphosphatase and guanylyltransferase – to the carboxyl terminus of the otherwise nonfunctional Rpb1-CTD-S5A protein.
To our delight, the experiment worked, i.e., an – The fact that four of the five phosphoacceptor coding letters of the CTD heptad are not essential in fission yeast raises important questions as to whether and how these phosphate marks impact gene expression, the extreme situations being that absence of a particular CTD-PO mark has little or no effect, or that loss of a coding cue does exert significant effects albeit on the expression of genes that are not essential under the laboratory conditions surveyed.