O. Bensaude et al., THE CARBOXY-TERMINAL DOMAIN (CTD) OF RNA- POLYMERASE-II PLAYS A PIVOTAL ROLE IN MESSENGER-RNA METABOLISM, MS. Medecine sciences, 14(2), 1998, pp. 167-174
RNA polymerase (RNAP) II is a multisubunit enzyme composed of several
different subunits. The largest subunit shows an intriguing carboxy-te
rminal domain (CTD) which consists in multiple repeats of a seven amin
o-acid motif. The same motif is-repeated 26 times in the yeast protein
and up to 52 times in the mammalian protein. An unphosphorylated CTD
is essential for the assembly of RNA polymerase and general transcript
ion factors into a preinitiation complex of transcription on promoters
. Phosphorylation of the CTD by the transcription factor TFIIH is requ
ired to elongate transcription, but other CTD kinases may also contrib
ute to it. The CTD is also required for pre-mRNA splicing and polyaden
ylation. But in this case, phosphorylation of the CTD is necessary to
associate the splicing machinery. In cells, the phosphorylation status
of the CTD of the largest subunit is tightly regulated by a balance b
etween protein kinases and phosphatases. Environmental and development
al programs influence this balance and may thus directly influence the
overall mRNA metabolism.