Seven Ups the Code

摘要

Patterns of phosphorylation in a region of RNA polymerase II may constitute a code that controls the recruitment of regulatory factors to control gene expression. Eukaryotic RNA polymerase II, the enzyme that converts DNA information into RNA, couples this transcrip-tional activity to both modifying the DNA template (chromatin) and to processing nascent RNA transcripts into mature forms. Proteins that carry out the latter two functions are tethered to the catalytic core of polymerase Ⅱ by a flexible carboxyl-terminal domain (CTD) that harbors tandem repeats of the consensus amino acid sequence Tyr~1-Ser~2-Pro~3-Thr~4-Ser~5-Pro~6-Ser~7 (7-3). Actively transcribing palymerase Ⅱ is phosphorylated on different sites within this heptapeptide sequence, and the pattern of phosphorylation has been proposed as a code that controls the binding of different regulatory factors to the enzyme (4). Two papers in this issue, by Chapman et al. on page 1780 (5) and by Egloff et al. on page 1777 ( < 5), provide evidence that expands the number of potential CTD phosphorylation states, supporting the notion of a CTD code. Together, the papers show that CTD phosphorylation is more complicated than previously thought and link, for the first time, expression of specific genes with a distinct CTD phosphorylation pattern.