A paper from Mike Harris in the de Bruin lab http://www.ncbi.nlm.nih.gov/pubmed/23593391 just showed SBF binding on the Swi4 promoter in yeast. So the central TF of the G1/S transition sits on its own promoter, just like E2F1-3 binding on the E2F1 promoter in mammalian cells. This continues the uncanny likeness between the yeast and mammalian G1 control networks despite lack of conservation at the level of protein sequence (see Cross, Buchler and Skotheim http://www.ncbi.nlm.nih.gov/pubmed/22084380). We decided to go back and analyze SWI4 in the context of transcription timing as discussed our paper Eser et al 2011. It turns out the data for SWI4 in our CDC20 block release experiments were not good so we could not reliably detect transcriptional activation times. However, in the G1 block-release experiments we do see nice early activation of SWI4 transcription consistent with Mike's data and consistent with our feedback-first model in which we predict feedback loop elements responsible for cell cycle commitment get activated prior to other co-regulated genes. Nice!

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AuthorJan Skotheim