The Role of Chromatin in Repeat Induced Transcriptional Repression (a) Primer extension products are shown from run-off RNA transcripts performed in vitro using a Hela cell nuclear extract incubated with pHSVtkCAT, in vitro CpG methylated pHSVtkCAT, pHSVtkCAT-(CGG)27, pHSVtkCAT-(CGG)70 and pHSVtkCAT-(CGG)105 DNAs. All reactions included control of pCMV-CAT DNA. (b) A graphical representation of the detectable transcript in the Helascribe reaction. The transcription was normalised to CMV-CAT as an internal control. (c) Primer extension analysis of the pHSVtkCAT-(CGG)140 reporter and pCMV-CAT injection control. Injections were of 5 ng reporter and 0.3 ng injection control per oocyte. The injected oocyte populations were incubated for 18 hours in the presence of 30 nM TSA. The primer extension products are shown with arrows and include the endogenous H4 message as an mRNA preparation control.