Coordinated increase in cellular RNA and protein content induced by overexpression of Far1, a cyclin dependent kinase inhibitor, involves large transcriptional reprogramming and requires the Sfp1 protein.

The FAR1 gene encodes a large protein, whose major function is inhibition of cyclin-dependent kinase complexes involved in the G1/S transition. It has been proposed that Far1, together with the G1 cyclin Cln3, may be part of a cell sizer mechanism that controls the entry into S phase. A genome-wide transcriptional analysis of FAR1-overexpressing and far1 deleted cells grown in ethanol- or glucose-supplemented minimal media indicates that FAR1 overexpression induces strong transcriptional remodelling, metabolism being the most affected cellular property. These data suggest that the Far1/Cln3 sizer regulates cell growth either directly or indirectly by affecting metabolism and pathways known to modulate ribosome biogenesis. A crucial role in mediating the effect of Far1 overexpression is played by the Sfp1 protein, a key transcriptional regulator of ribosome biogenesis, whose presence is mandatory to allow a coordinated increase in both RNA and protein levels in ethanol-grown cells.

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