Satellite DNA is transcribed on lampbrush chromosomes

Abstract

During the lampbrush stage of oogenesis there is widespread transcription, and it has been estimated that the total amount of DNA transcribed may be an order of magnitude greater than that required to produce the necessary functional RNA for the oocyte. We therefore considered it likely that some of the transcribed sequences have little, if any, translational significance, and may include both middle repetitive and highly repeated, or satellite, sequences. Satellite DNA is generally defined as rapidly reannealing DNA which has a short basic sequence that is repeated millions of times in the genome, usually in tandem arrays. The short repeated length, coupled with the organisation of satellite sequences in high order molecular weight tandem arrays in heterochromatic regions, have been put forward as reasons for supposing that this type of DNA is not normally transcribed. We report here that we have looked for and found evidence of transcription of satellite DNA on lampbrush loops in oocytes of the crested newt, Triturus cristatus carnifex.