In vivo and in vitro interaction between human transcription factor MOK2 and nuclear lamin A/C.

The human and murine MOK2 proteins are factors able to recognize both DNA and RNA through their zinc finger motifs. This dual affinity of MOK2 suggests that MOK2 might be involved in transcription and post-transcriptional regulation of MOK2 target genes. The IRBP gene contains two MOK2-binding elements, a complete 18 bp MOK2-binding site located in intron 2 and the essential core MOK2-binding site (8 bp of conserved 3'-half-site) located in the IRBP promoter. We have demonstrated that MOK2 can bind to the 8 bp present in the IRBP promoter and repress transcription from this promoter by competing with the CRX activator for DNA binding. In this study, we identify a novel interaction between lamin A/C and hsMOK2 by using the yeast two-hybrid system. The interaction, which was confirmed by GST pull-down assays and co-immunolocalization studies in vivo, requires the N-terminal acidic domain of hsMOK2 and the coiled 2 domain of lamin A/C. Furthermore, we show that a fraction of hsMOK2 protein is associated with the nuclear matrix. We therefore suggest that hsMOK2 interactions with lamin A/C and the nuclear matrix may be important for its ability to repress transcription.