Conservation of the mammalian RNA polymerase II largest-subunit C-terminal domain

Summary We have isolated and sequenced a portion of the gene encoding the carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II from three mammals. These mammalian sequences include one rodent and two primate CTDs. Comparisons of the new sequences to mouse and Chinese hamster show a high degree of conservation among the mammalian CTDs. Due to synonymous codon usage, the nucleotide differences between hamster, rat, ape, and human result in no amino acid changes. The amino acid sequence for the mouse CTD appears to have one different amino acid when compared to the other four sequences. Therefore, except for the one variation in mouse, all of the known mammalian CTDs have identical amino acid sequences. This is in marked contrast to the situation among more divergent species. The present study suggests that there is a strong evolutionary pressure to maintain the primary structure of the mammalian CTD. Offprint requests to: J.L. Corden     

The diverse roles of RNA polymerase II C-terminal domain phosphatase SCP1

RNA polymerase II carboxyl-terminal domain (pol II CTD) phosphatases are a newly emerging family of phosphatases that are members of DXDX (T/V). The subfamily includes Small CTD phosphatases, like SCP1, SCP2, SCP3, TIMM50, HSPC129 and UBLCP. Extensive study of SCP1 has elicited the diversified roles of the small C terminal domain phosphatase. The SCP1 plays a vital role in various biological activities, like neuronal gene silencing and preferential Ser5 dephosphorylation, acts as a cardiac hypertrophy inducer with the help of its intronic miRNAs, and has shown a key role in cell cycle regulation. This short review offers an explanation of the mechanism of action of small CTD phosphatases, in different biological activities and metabolic processes. [BMB Reports 2014; 47(4): 192-196]     

RNA polymerase II acts as an RNA‐dependent RNA polymerase to extend and destabilize a non‐coding RNA

RNA polymerase II (Pol II) is a well‐characterized DNA‐dependent RNA polymerase, which has also been reported to have RNA‐dependent RNA polymerase (RdRP) activity. Natural cellular RNA substrates of mammalian Pol II, however, have not been identified and the cellular function of the Pol II RdRP activity is unknown. We found that Pol II can use a non‐coding RNA, B2 RNA, as both a substrate and a template for its RdRP activity. Pol II extends B2 RNA by 18 nt on its 3′‐end in an internally templated reaction. The RNA product resulting from extension of B2 RNA by the Pol II RdRP can be removed from Pol II by a factor present in nuclear extracts. Treatment of cells with α‐amanitin or actinomycin D revealed that extension of B2 RNA by Pol II destabilizes the RNA. Our studies provide compelling evidence that mammalian Pol II acts as an RdRP to control the stability of a cellular RNA by extending its 3′‐end.     

DNA-dependent RNA polymerase II from nuclei of suspension-cultured tobacco cells

From isolated nuclei of suspension cultured cells of Nicotiana tabacum. DNA-dependent RNA polymerase II (E.C. 2.7.76) has been purified to homogeneity as evidenced by polyacrylamidegel electrophoresis under non-denaturing conditions. The purified enzyme had a specific activity of more than 15 nmol min^-1·mg^-1 with denatured calf thymus DNA as template. Sodium-dodecyl-sulfate gel electrophoresis and protein highperformance liquid chromatography revealed a subunit composition of four proteins with molecular weights of 165 000, 135 000, 35 000 and 25 000 and with a stoichiometry of 1:1:2:2. The RNA polymerase did not exhibit any detectable proteinkinase activity. The 25 000 subunit binds ADP in a molar ratio of 1:1; it could not be decided whether this subunit has an ATPase activity or is merely an acceptor of ADP.Abbreviations HPLC high-performance liquid chromatography - PMSF phenylmethylsulfonyl fluoride - SDS sodium dodecyl sulfate This contribution is dedicated to Professor Fritz Cramer on the occasion of his 60th birthday     

INTAC endonuclease and phosphatase modules differentially regulate transcription by RNA polymerase II

1. Download : Download high-res image (251KB)
2. Download : Download full-size image