Nazareth Bastajian
(Graduate Student, PhD Candidate)

I am interested in how G1 transcription is regulated.  In the late G1 phase of budding yeast, at a point termed Start, many genes, including CLN2, are induced in one large transcriptional cluster.  This induction is important for the cell to transit G1 phase in order to undergo a new round of cell division.  The heterodimeric transcription factors SBF and MBF contribute strongly to this burst of gene expression.  It has been hypothesized that upstream factors regulate SBF and MBF activity in late G1 phase.  The genetic evidence suggests that Cln3 and Bck2 are two key regulators of G1 transcription, although other there are likely other regulators not yet identified.  Equally unclear are the mechanisms by which regulation of G1 transcription occurs.  For instance, we do not yet know the mechanisms by which Bck2 can activate CLN2 transcription in both an SBF/MBF-dependent and independent manner. I am interested in genes important for transactivation of the key G1-specific gene CLN2 that is important for transit through G1.  Using SGA technology I have identified strains defective for G1 transcription by scoring strains defective in activation of CLN2-lacZ reporter constructs.  Using a biochemical approach, I have developed an affinity capture assay to quickly screen for physical interactions, in vitro, between SBF or MBF and putative G1 transcriptional regulators identified from my genomic screens.  Using these two complimentary approaches, it is feasible to flesh out our framework of how G1 transcription occurs.