Characterization of the telomere complex, TERF1 and TERF2 genes in muntjac species with fusion karyotypes.
The telomere binding proteins TRF1 and TRF2 maintain and protect chromosome ends and confer karyotypic stability. Chromosome evolution in the genus Muntiacus is characterized by numerous tandem (end-to-end) fusions. To study TRF1 and TRF2 telomere binding proteins in Muntiacus species, the authors isolated and characterized the TERF1 and -2 genes from Indian muntjac (Muntiacus muntjak vaginalis; 2n = 6 female) and from Chinese muntjac (Muntiacus reevesi; 2n = 46). Expression anal. revealed that both genes are ubiquitously expressed and sequence anal. identified several transcript variants of both TERF genes. Control expts. disclosed a novel testis-specific splice variant of TERF1 in human testes. Amino acid sequence comparisons demonstrate that Muntiacus TRF1 and in particular TRF2 are highly conserved between muntjac and human. In vivo TRF2-GFP and immunostaining studies in muntjac cell lines revealed telomeric TRF2 localization, while deletion of the DNA binding domain abrogated this localization, suggesting muntjac TRF2 represents a functional telomere protein. Finally, expression anal. of a set of telomere-related genes revealed their presence in muntjac fibroblasts and testis tissue, which suggests the presence of a conserved telomere complex in muntjacs. However, a deviation from the common theme was noted for the TERT gene, encoding the catalytic subunit of telomerase; TERT expression could not be detected in Indian or Chinese muntjac cDNA or genomic DNA using a series of conserved primers, while TRAP assay revealed functional telomerase in Chinese muntjac testis tissues. This suggests muntjacs may harbor a diverged telomerase sequence.
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