engleski

RNA Pol II Promotes Transcription of Centromeric Satellite DNAs in Beetles

Transcripts of centromeric satellite DNAs are known to play a role in heterochromatin formation as well as in establishment of the kinetochore. However, little is known about basic mechanisms of satellite DNA expression within constitutive heterochromatin and its regulation. Here we present comprehensive analysis of transcription of abundant pericentromeric satellite DNAs from beetles (Coleoptera), PRAT from Palorus ratzeburgii and TCAST from Tribolium castaneum. Both satellites are expressed in all three developmental stages at similar level. Transcripts are abundant and heterogeneous in size ranging from 0.5 kb up to more than 5 kb. Transcription proceeds from both strands but with 10 fold different expression intensity and transcripts are not processed into siRNAs. Multiple, irregularly distributed transcription initiation sites as well as termination sites have been mapped within the PRAT and TCAST sequences. The presence of cap structure and poly(A) tails in a portion of the transcripts as well as sensitivity to alpha-amanitin indicate RNA polymerase II – dependent transcription. There is strong indication that both satellite DNAs are transcribed as autonomous transcription units from own promoters that reside within satellite sequences. Transcripts remain in the nucleus and are proposed to play a structural role in the formation of kinetochore.

heterochromatin transcription ; centromere

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