The telomeric protein Rap1 is conserved in vertebrates and is expressed from a bidirectional promoter positioned between the Rap1 and KARS genes

We have identified the chicken homolog of the mammalian telomere protein repression and activation protein I (Rap1). Although cRap1 has only 36% sequence identity to hRap1, it contains the same conserved BRCA1 C-terminal (BRCT), Myb and Rap C-terminus (RCT) domains. Two-hybrid analysis and immunolocalization experiments revealed that cRap1 interacts with the telomere-binding protein telomeric repeat binding factor (TRF)2 and localizes to telomeres. Thus, despite considerable sequence divergence, the identity and overall domain structure of telomere-associated proteins is conserved in vertebrates. Analysis of the cRap1 genomic locus revealed that the cRap I gene lies immediately adjacent to the cKARS (lysyl-tRNA synthetase) gene with the two genes in a head-to-head orientation separated by only 57 nt. This same organization is conserved at the human Rap1-KARS locus. When 5' regions of the cRap I and cKARS genes were tested for promoter activity, the promoters of both genes were found to lie in or near the intergenic spacer. The two promoters lack TATA boxes but appear to have downstream promoter elements (DPEs). Analysis of human Rap I and KARS expressed sequence tags (ESTs) indicated that this localization of TATA-less promoters to the intergenic spacer is a conserved feature of the Rap1-KARS locus. (C) 2003 Elsevier B.V. All rights reserved.