| First Author | Stains JP | Year | 2005 |
| Journal | Biochem J | Volume | 385 |
| Issue | Pt 2 | Pages | 613-23 |
| PubMed ID | 15361071 | Mgi Jnum | J:117520 |
| Mgi Id | MGI:3696637 | Doi | 10.1042/BJ20040680 |
| Citation | Stains JP, et al. (2005) Heterogeneous nuclear ribonucleoprotein K represses transcription from a cytosine/thymidine-rich element in the osteocalcin promoter. Biochem J 385(Pt 2):613-23 |
| abstractText | HnRNP K (heterogeneous nuclear ribonucleoprotein K) was biochemically purified from a screen of proteins co-purifying with binding activity to the osteocalcin promoter. We identify hnRNP K as a novel repressor of osteocalcin gene transcription. Overexpression of hnRNP K lowers the expression of osteocalcin mRNA by 5-fold. Furthermore, luciferase reporter assays demonstrate that overexpression of hnRNP K represses osteocalcin transcription from a CT (cytosine/thymidine)-rich element in the proximal promoter. Electrophoretic mobility-shift analysis reveals that recombinant hnRNP K binds to the CT-rich element, but binds ss (single-stranded), rather than ds (double-stranded) oligonucleotide probes. Accordingly, hnRNP K antibody can supershift a binding activity present in nuclear extracts using ss sense, but not antisense or ds oligonucleotides corresponding to the CT-rich -95 to -47 osteocalcin promoter. Importantly, addition of recombinant hnRNP K to ROS 17/2.8 nuclear extract disrupts formation of a DNA-protein complex on ds CT element oligonucleotides. This action is mutually exclusive with hnRNP K's ability to bind ss DNA. These results demonstrate that hnRNPK, although co-purified with a dsDNA-binding activity, does not itself bind dsDNA. Rather, hnRNP K represses osteocalcin gene transcription by inhibiting the formation of a transcriptional complex on the CT element of the osteocalcin promoter. |
