Updating the rna polymerase ctd code
To explore this issue, we applied high-throughput RNA sequencing methods (RNAseq) to gauge globally the impact of the loss of each of the four inessential CTD phosphoacceptors on gene expression.
This analysis (a collaboration with Jürg Bähler’s lab) illuminated how individual letters of the Pol2 CTD code affect the expression of limited and distinct sets of genes: to wit, CTD mutations elicited increased expression of genes encoding proteins involved in iron uptake (Frp1, Fip1, Fio1, Str3, Str1, Sib1, etc.), without affecting the expression of the genes that repress the iron regulon, implying that Tyr1-Ser2 transduces a repressive signal in iron homeostasis.
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?Recent studies show that the two remaining potential phosphorylation sites, tyrosine-1 and threonine-4, are phosphorylated as well and contribute to the previously proposed "CTD code".With the impairment of binding of CTD interacting factors, these novel phosphorylation marks add an accessory layer of regulation to the RNAP II transcription cycle.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.