engleski

Transcription of satellite DNAs and genome regulation in Tribolium beetles

The very complex life cycle and extreme diversity of insect life forms require a carefully regulated network of biological processes to switch on and off the right genes at the right time. Chromatin condensation is a way of gene silencing, as evident for the hundreds of functional protein genes harboured in heterochromatic regions of different insect species. Being the major heterochromatin constituents in beetle genera Tribolium and Palorus (Coleoptera), satellite DNA sequences are supposed to play important roles in heterochromatin regulation. RNA Pol II transcription from pericentromeric satellite DNA elements occurs in all developmental stages of beetle Tribolium castaneum, being the highest during embryogenesis. Transcription proceeds from both DNA strands in the form of long heterogeneous size transcripts ranging in size from 500 bp to more than 5 kb. Transcripts are processed into small RNAs that are 19 to 26 nt long. Satellite DNA transcripts are not polyadenylated and preferentially remain in the nucleus. Presence of multiple transcription initiation sites and putative promoter elements within satellite monomer gives strong indication that satellite DNA is transcribed as autonomous transcription unit from own promoters. Expression of satellite DNA is temperature sensitive during embryogenesis being significantly decreased at low temperatures where development is stopped. It can be proposed that the change in satellite DNA expression affects heterochromatin formation during embryogenesis and in this way influences activity of heterochromatin-localized developmental genes. Temperature –sensitive expression of heterochromatic satellite DNAs indicates also their involvement in the signalling mechanism responsible for insect development, differentiation and environmental stress response.

satellite DNA; non-coding RNA

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