What downregulation of the genes TP53 and CASP3 stands for???

[Kobrus]

Hello!

I am investigating apoptosis by applying qRT-PCR technique.
I have done qRT-PCR and gotten downregulation on mRNA level of TP53 and CASP3 genes in the tissue exposed to UVR. Downregulation follows by the upregulations of the genes!
I am wondering what the mechanisms behind the genes' downregulation can be in this case?!

Thank you!

[Warthaug]

If I had to guess, UV is damaging the RNA, and it is being degraded as a consequence. UV damage also increases expression of these genes, leading to the upregulation you are observing later on.

Have you compared this to an RNA whose levels should be consistent? If I am correct, you should see down-regulation of most/all RNAs in the cell. If I'm wrong than I have no idea why you are seeing what you are seeing.

Sorry I couldn't be of more help.

Bryan

[Kobrus]

Thank you, Bryan, for your reply!

I did expose rat lenses to in vivo UVR-B, then ran evolution study with the latest latency of 5 days. Lenses cDNAs (exposed and control) were amplified with relative qRT-PCT using p53-, caspase-3 and gadd45 primers. I used 18s as a reference gene.

18s cDNA input was indifferent between exposed and control lenses likewise for gadd45 in all time intervals. p53 mRNA upregulation precedes caspase3 upregulation in the rat lens after in vivo exposure to UVR. Both TP53 and CASP3 genes are downregulated in early latencies.
It might be so that UV degrades mRNA but not really 18s rRNA as I see. I found also in P.C.Hanawalt papers that recovery of mRNA synthesis following by UVR and transcription-coupled repair (TCR) take places in DNA damaged tissues, so that perhaps I do have degradation of mRNA in earlier latencies followed by recovery of mRNA synthesis and upregulation of mRNAs.
But then, I do not observe differences in all time intervals for gadd45. Do you have any idea why?? It's mRNAs should degrade also like p53 etc. Perhaps, gadd45 upregulation on mRNA level should come later, after 5 days..

Thank you!!!