Primary/Secondary Effects: Temperature-sensitive mutants
The reduction in mRNA levels observed in temperature sensitive (ts) mutants soon after a temperature shift (i.e., 45 minutes) is likely due to primary effects because of the time required to produce most secondary effects involves a substantial reduction in both a transcript and its translation product. Nonetheless, the results obtained in this type of experiment must be regarded as the sum of primary and secondary effects of factor inactivation. We have devised a method to identify the set of genes whose change in expression is almost certainly a direct consequence of the loss of function of the temperature sensitive factor. This involves comparing data from ts inactivation of RNA polymerase II with that obtained by ts inactivation of any other factor.
The fold-reduction in all transcripts has been determined for the RNA polymerase II temperature sensitive mutant rpb1-1 relative to its isogenic wild-type counterpart 45 minutes after a shift to 37°C. The same data is collected for another ts mutant exposed to identical experimental conditions. Comparison of the two data sets reveals the set of transcripts with equivalent decay kinetics in rpb1-1 and another ts mutant (more detail). This method identifies the set of genes whose expression is equivalently dependent on the factor of interest and RNA polymerase II itself.
For researchers who wish to study specific genes which are most likely directly regulated through the function of a specific transcription factor, the following lists have been generated.
Genes probably directly regulated by: