Chromosomally-retained RNA mediates homologous pairing

Pairing and recombination of homologous chromosomes are essential for ensuring correct segregation of chromosomes in meiosis. In S. pombe, chromosomes are first bundled at the telomeres (forming a telomere bouquet) and then aligned by oscillatory movement of the elongated “horsetail” nucleus (Fig. 1).(1)(,)(2) Telomere clustering and subsequent chromosome alignment promote pairing of homologous chromosomes.(3)(-)(5) However, this telomere-bundled alignment of chromosomes cannot be responsible for the specificity of chromosome pairing. Thus, there must be some mechanism to facilitate recognition of homologous partners after telomere clustering. Recent studies in S. pombe have shown that RNA transcripts retained on the chromosome, or RNA bodies, may play a role in recognition of homologous chromosomes for pairing (Fig. 1).(6) Acting as fiducial markers of homologous loci they would abrogate the need for direct DNA sequence homology searching.