The synthesis of authentic sea urchin transcriptional and translational products by sea urchin histone genes injected into Xenopus laevis oocytes (original) (raw)

We have analyzed the transcriptional and translational products of recombinant plasmids containing the sea urchin histone genes following their injection into the germinal vesicle (GV or oocyte nucleus) of Xenopus laeuis oocytes. Plasmids pSp2 and pSplO2 contain the identical sea urchin DNA fragment with the Hl, H2B, and H4 histone protein coding regions and adjacent spacer sequences, but are inserted in different vectors. The plasmid, pRC 39, contains only that segment of the pSp2 eucaryotic fragment corresponding to the sea urchin H2B gene plus 125 base pairs of the "upstream" spacer sequences. The translational products produced under the direction of pSp2 and pSplO2 comigrate with authentic sea urchin Hl and H2B histones in a two-dimensional gel system. Since sea urchin H4 histone protein comigrates with endogenous Xenopus H4 histone. the synthesis of the sea urchin protein could not be confirmed. The transcriptional products observed in oocytes injected in the GV with plasmids pSp2 and pSplO2 hybridize to a radioactively labeled DNA probe produced from the Hl, H2B, and H4 sea urchin histone genes, and comigrate with several of the authentic sea urchin histone mRNAs on polyacrylamide gels under denaturing conditions. These results suggest that the injected sea urchin histone genes are being transcribed properly and are producing functional histone mRNAs in Xenopus oocytes. We calculate that the injected genes are being transcribed at approximately 0.1 transcript per gene per hour. This represents IO7 to 10" transcripts or approximately 0.1% of the total transcriptional activity of stage 6 oocytes. We do not detect proper transcriptional or translational products when plasmid pRC 39 is injected into the GVs of Xenopus oocytes. This result suggests that the eucaryotic fragment present in this plasmid may not contain the information for proper expression of the sea urchin H2B gene.