Bioassay for components regulating eukaryotic gene expression: a chromosomal factor involved in the generation of histone mRNA 3' termini.

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Abstract
The oocyte injection procedure was adopted for the detection of regulatory components involved in the transcription of a eukaryotic mRNA gene. Injection of the histone gene repeat h22 DNA of Psammechinus miliaris into the Xenopus oocyte nucleus results in correct initiation of the histone mRNA, but readthrough by RNA polymerase occurs at the 3'' end of the H3 histone gene. Coinjection into the oocyte of a chromosomal salt wash fraction derived from sea urchin embryos results in the generation of authentic 3'' termini of the histone H3 mRNA. The protein component was partially purified by column chromatography and density gradient centrifugation. The regulatory factor binds to heparin columns and, hence, has the properties anticipated of an RNA- or DNA-binding protein. The sedimentation coefficient of the active component was determined to be about 12S, suggesting a MW of 200,000-250,000.