Association of human DNA helicase RecQ5beta with RNA polymerase II and its possible role in transcription.

Although RecQ5beta is a ssDNA (single-stranded DNA)-stimulated ATPase and an ATP-dependent DNA helicase with strand-annealing activities, its cellular function remains to be explored. In the present paper, we used immunopurification and MS-based analyses to show that human DNA helicase RecQ5beta is associated with at least four RNAP II (RNA polymerase II) subunits. RecQ5beta was also present in complexes immunoprecipitated using three different antibodies against the large subunit of RNAP II, or in complexes immunoprecipitated using an anti-FLAG antibody against either FLAG-RNAP II 33 kDa subunit or FLAG-Pin1. Different regions of the non-helicase domain of the RecQ5beta molecule were associated with hypophosphorylated and hyperphosphorylated forms of the RNAP II large subunit independently of DNA and RNA. RecQ5beta was also found in nuclear chromatin fractions and associated with the coding regions of the LDL (low-density lipoprotein) receptor and beta-actin genes. Knockdown of the RecQ5beta transcript increased the transcription of those genes. The results of the present study suggest that RecQ5beta has suppressive roles in events associated with RNAP II-dependent transcription.