James K. Skipper

Counterproductive transcriptional and translational regulation of elongation factor 1-α synthesis during early development in sea urchins

We have isolated a cDNA clone encoding elongation factor 1-alpha (EF1-alpha) and used probes prepared from this cDNA to measure levels of EF1-alpha transcripts during early development. We also determined the fraction of EF1-alpha transcripts in polysomes during this time period. Following the blastula stage there is a sharp increase in the amount of EF1-alpha mRNA. This pattern of accumulation is similar to other previously described sea urchin mRNAs. However, while the level of EF1-alpha mRNA is increasing, the fraction of EF1-alpha mRNA in polysomes decreases. Thus, there is an apparently counter-productive decrease in efficiency of recruitment into polysomes occurring concurrently with an increase in the overall amount of EF1-alpha mRNA.

Identification of two forms of progesterone receptor from chick oviduct cytosol using non-denaturing gel electrophoresis☆

Non-denaturing polyacrylamide gel electrophoresis and non-denaturing agarose gel electrophoresis have been used to resolve [3H]R5020-binding components from chick oviduct cytosol. From both gel systems 2 peaks of bound radioactivity are resolved which display these properties of authentic progesterone receptor: binding of R5020: steroid specificity, saturability, and restriction to target tissues. The two peaks are approximately equal in magnitude, and there is no evidence for interconversion of the 2 peaks. The presence or absence of 10-20 mM sodium molybdate during cytosol preparation had no effect on the magnitude or mobility of either peak. Neither peak contains salt-dissociable components which affect its electrophoretic properties, suggesting a possible alteration of native receptor forms during electrophoresis.