Transcription of a satellite DNA in the newt.

Abstract

Satellite 2 is an abundant, 330-bp tandemly repeated sequence in the genome of the newt, Notophthalmus viridescens. This sequence is distributed throughout the genome on each of the 11 chromosomes. Both strands of satellite 2 are transcribed on the lampbrush chromosomes during oogenesis, probably as a result of readthrough from upstream structural gene promoters. In addition to these heterogeneous nuclear transcripts, satellite 2 is homologous to stable, strand-specific cytoplasmic transcripts in a variety of different tissues. The majority of these transcripts correspond in size to the entire satellite 2 repeat unit, or to whole multiples of the repeat. The transcripts present in the ovary have been sequenced by primer extension and were found to be more homogeneous than eight independently cloned satellite 2 DNA repeats. We propose that the stable cytoplasmic transcripts are encoded by a small subset of genomic satellite 2 sequences.