MOLECULAR-CLONING AND CHROMOSOMAL LOCALIZATION OF CHINESE-HAMSTER TELOMERIC PROTEIN CHTRF1 - ITS POTENTIAL ROLE IN CHROMOSOMAL INSTABILITY

Chinese hamster cells frequently have altered karyotypes, To investiga te the basis of recent observations that karyotypic alterations are re lated to telomeric fusions, we asked whether these alterations are due to lack of telomere repeat binding factor/s, Further, Chinese hamster chromosomes contain large blocks of interstitial telomeric repeats, w hich are preferentially involved in chromosome breakage and exchange, rendering it an interesting model for such studies. Here, we report on the cloning and the chromosomal localization of the Chinese hamster t elomere repeat binding factor, chTRF1, The sequence analysis revealed, similar to human TRF1 (hTRF1), an N-terminal acidic domain, a TRF1 sp ecific DNA binding motif and a C-terminal Myb type domain, Unlike mous e TRF1 (mTRF1), chTRF1 shows 97.5% identity to hTRF1, chTRF1 gene was localized on the long arm of chromosome 5. In vitro translation of chT RF1 resulted in protein product similar in molecular weight to hTRF1, Immunostaining of Chinese hamster ovary cells (CHO) with anti-TRF1 ant ibody revealed punctate nuclear staining. At metaphase, antibodies fai led to detect TRF1 on most of the chromosome ends and the interstitial telomeric repeat bands. These studies suggest that chTRF1 does not bi nd the interstitial telomeric repeats, and its presence at the metapha se chromosome ends is limited. The later could be a factor contributin g to frequent karyotypic alterations observed in Chinese hamster cells .