Abstract
Two subunits in RNA polymerase II (e.g. RPB3 and RPB11 in yeast) and two subunits common to RNA polymerases I and III (e.g. AC40 and AC19 in yeast) contain one or two motifs related to the alpha subunit in prokaryotic RNA polymerases. We have sequenced two different cDNAs (AtRPB36a and AtRPB36b), the two corresponding genes from Arabidopsis thaliana that are homologs of yeast RPB3, and an Arabidopsis cDNA (AtRPB13.6) that is a homolog of yeast RPB11. The B36a subunit is the predominant B36 subunit associated with RNA polymerase II purified from Arabidopsis suspension culture cells, and this subunit has a stoichiometry of about 1. Results from protein association assays showed that the B36a and B36b subunits did not associate, but each of these subunits did associate with the B13.6 subunit in vivo and in vitro. Two motifs in the B36b subunit related to the prokaryotic alpha subunit were shown to be required for the in vitro interactions with the B13.6 subunit. Our results suggest that the B36 and B13.6 subunits associate to form heterodimers in Arabidopsis RNA polymerase II like the AC40 and AC19 heterodimers reported for yeast RNA polymerases I and III but unlike the B44 homodimers reported for yeast RNA polymerase II.
Highlights
We report on the cloning and sequencing of genes and/or cDNAs for the 36-kDa (B36a and B36b) and 13.6-kDa (B13.6) subunits in Arabidopsis RNA polymerase II, which are homologs to yeast B44 and B12.5, respectively, to determine the stoichiometry of the B36 subunit in the enzyme and investigate its self-association and its association with the B13.6 subunit
Our results have shown that Arabidopsis contains two genes that encode the third largest subunit of RNA polymerase II
The two genes are expected to encode the third largest subunit in RNA polymerase II, based on stronger homology to the third largest subunit in yeast and human RNA polymerase II and lesser homology to a related subunit in yeast and mouse RNA polymerases I and III. This is supported by our cloning of two additional cDNAs from Arabidopsis that encode proteins that show stronger homology to the yeast and mouse AC40 subunits in RNA polymerases I and III than to the yeast RPB3 or human hRPB33 subunit in RNA polymerase II [46]
Summary
Yeast RNA polymerase II contains a total of 12 subunits, and each of these is encoded by a single copy gene Studies on mutations in the three largest subunits of yeast RNA polymerase II indicate that the B44 subunit associates with second largest subunit (i.e. B150 or RPB2), which in turn complexes with the largest subunit (i.e. B220 or RPB1) to facilitate assembly of the enzyme [18]. We report on the cloning and sequencing of genes and/or cDNAs for the 36-kDa (B36a and B36b) and 13.6-kDa (B13.6) subunits in Arabidopsis RNA polymerase II, which are homologs to yeast B44 and B12.5 (i.e. encoded by the RPB3 and RPB11 genes in S. cerevisiae), respectively, to determine the stoichiometry of the B36 subunit in the enzyme and investigate its self-association and its association with the B13.6 subunit
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
