Toward an Understanding of Satellite DNA Function in Crustacea1

SYNOPSIS. A G+C-rich satellite DNA (stDNA) in Gecarcinus lateralis with a repeat unit of 2.1 kbp makes up approximately 3 % (16,000 copies/nucleus) of the land crab genome. We used sequences from conserved domains of the repeat unit to construct probes for exploring the possibility of the repeat units being transcribed into RNA, their distribution in genomic DNA, and their methylation status. A transcription product hybridizing with TRU-EXON, a region of the satellite bor-dered by possible exon splice junctions, was found only in land crabs, whereas transcription products that hybridized to 3'END, a 368 bp fragment at the 3'-end of the satellite, were also found in several other crustaceans. Transcription prod-ucts that hybridized to AMPL-3, a probe from an amplified segment of the satellite, were not found in land crabs but were found in lobsters. In land crabs, several poly(A)+RNA transcripts that hybridized to 3'END were specific for DNA strand, tissue, and intermolt stage. The diversity of transcripts suggests that transcription of the satellite is related to the organization of the repeated DNA in the crab genome, and that some satellite domains may be transcribed because of their po