Synaptonemal complexes from DNase-treated rat pachytene chromosomes contain (GT)n and LINE/SINE sequences

Abstract

Purified chromosome cores (synaptonemal complexes) of rat pachytene chromosomes, from which the chromatin is removed by extensive DNase II digestion, retain a residual class of DNA, presumably the bases of chromatin loops. This synaptonemal complex-associated DNA, isolated by proteinase digestion and phenol extraction of purified DNase-treated synaptonemal complexes, and cloned in plasmid vector pEMBL18, has a length distribution of 50-500 bp. From a library of these fragments, 21 fragments were sequenced. Present in this sample are short 40-200-bp segments with greater than 80% identity to "long" and "short" interspersed repeated elements (LINE/SINEs), an excess of GT/CA tandem repeats and a number of unidentified sequences. The LINE/SINE segments may play a role in homology vs. nonhomology recognition during meiosis and the alternating purine-pyrimidine sequences have been implicated in genetic recombination. Their enrichment in synaptonemal complexes may be related to the synapsis and recombination functions of meiosis.