Abstract
It is well documented that the snRNP particles play a role in the processing of histone pre-mRNAs. There is also evidence that in addition to the snRNP particles, at least two more proteins are involved in the in vitro 3′-processing of histone pre-mRNAs. The aim of the present work was the isolation and purification of one of these PF250 factors. Processing factor PF250 was isolated from HeLa nuclear extracts using ion exchange chromatography. Its ability to partially restore the processing activity of heat inactivated nuclear extract was demonstrated in vitro using labelled H4 pre-mRNA. Our results indicate that nuclear extracts exposed to 50°C for 15 min lacked any processing activity. Using a series of column chromatography purification steps we isolated a thermolabile protein factor that partially restored the activity of heat inactivated HeLa cell nuclear extracts. It can be concluded that besides U7 snRNP particles at least one more thermolabile protein factor is required for the maturation of H4 pre-mRNA in vitro. It has a molecular mass of 30 kDa and is inactivated by heating at 50°C. These characteristics make it a likely candidate to be a regulatory factor involved in pre-mRNA processing.
Published Version
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