Disease relevance of POLR2E

• Human RPB5, a subunit shared by eukaryotic nuclear RNA polymerases, binds human hepatitis B virus X protein and may play a role in X transactivation [1].

High impact information on POLR2E

• Our results support the idea that the interaction of HBx and human RPB5 can facilitate HBx transactivation and that human RPB5 has a domain which can communicate with transcriptional regulators [1].
• The HBx binding region of human RPB5 by itself stimulated chloramphenicol acetyltransferase activities from several different reporters having X-responsive element(s) [1].
• Interestingly, TIP120 also stimulates RNAP I- and III-driven transcription and binds to RPB5, one of the common subunits of the eukaryotic RNA polymerases, in vitro [2].
• To assess functional relatedness of individual components of the eukaryotic transcription apparatus, three human subunits (hsRPB5, hsRPB8, and hsRPB10) were tested for their ability to support yeast cell growth in the absence of their essential yeast homologs [3].
• Here, we show that four distantly related eukaryotic lineages (the higher plant and three protistan) have independently expanded their repertoire of RPB5 and RPB6 subunits [4].

Biological context of POLR2E

• Here we report systematic mutagenesis of the central part of RPB5 using two-step alanine scanning libraries to pinpoint critical residues for its binding to RAP30 in the TFIIF complex and/or to HBx, and identified these residues in both mammalian cells and in an in vitro binding assay [5].
• The RAP30-binding region was mapped to the central region (amino acids (aa) 47-120) of RPB5, which partly overlaps the hepatitis B virus X protein-binding region [6].
• The homology of the amino acid sequence is 55% and 43% with Saccharomyces cerevisiae RPB5 and human hRPB25, respectively [7].

Other interactions of POLR2E

• Within the intricate network of interactions, subunits hRPB3 and hRPB5 play a central role in polymerase organization [8].
• Scanning of the middle part of RAP30 by clustered alanine substitutions and then point alanine substitutions pinpointed two residues critical for the RPB5 binding in in vitro and in vivo assays [6].
• Further analysis of binding specificities showed that spTFIIEbeta binds the Rpb2 and Rpb12 subunits of PolII, whereas spTFIIEalpha predominantly binds Rpb5, which is located at the clamp region and changes conformation upon transcription initiation [9].

Analytical, diagnostic and therapeutic context of POLR2E

• The HBx transactivation domain and the central region of human RPB5 were necessary for the specific binding of the two proteins as shown by: (i) in vitro assays using deletion mutants of fusion proteins; (ii) in vivo assays which detect associated proteins by co-immunoprecipitation of the non-fused proteins from transfected HepG2 cells [1].

References