Satellite-tagged transcribing sequences in Bubalus bubalis genome undergo programmed modulation in meiocytes: Possible implications for transcriptional inactivation

We cloned and sequenced a 1378 bp BamHI satellite DNA fraction from the wat er buffalo Bubalus bubalis and have studied its expression in different tis sues. The GC-rich sequences of the resultant contig pDS5 crosshybridize onl y with bovid DNA and are not conserved evolutionarily. Typing of buffalo ge nomic DNA using pDS5 with several restriction enzymes revealed multilocus m onomorphic bands. Similar typing of cattle, buffalo, goat, sheep, and gaur genomic DNA revealed variations in copy number and allele length giving ris e to species-specific band patterns. Expression study of pDS5 in bubaline s amples by RNA slot-blot, Northern blot, and RT-PCR showed various levels of signal in all the somatic tissues and germline cells except heart. A GenBa nk database search revealed homology of pDS5 sequences in the 5' region fro m nt 1-1261 with collagen gene. An AluI typing analysis of DNA from bubalin e semen samples showed consistent loss of two bands. The presence of corres ponding bands in somatic tissues suggests a sequence modulation within the pDS5 array in meiocytes during spermatogenesis, which is restored in the so matic cells after fertilization. Modulation of the satellite-tagged transcr ibing sequence in the meiocytes may be a mechanism of its inactivation.