In yeast, inducible genes such as INO1, PRM1 and HIS4 reposition from the nucleoplasm to nuclear periphery upon activation. This leads to a physical interaction with nuclear pore complex (NPC), interchromosomal clustering, and stronger transcription. Repositioning to the nuclear periphery is controlled by cis-acting transcription factor (TF) binding sites located within the promoters of these genes and the TFs that bind to them. Such elements are both necessary and sufficient to control positioning of genes to the nuclear periphery. We have identified four TFs capable of controlling the regulated positioning of genes to the nuclear periphery in budding yeast under different conditions: Put3, Cbf1, Gcn4 and Ste12. Gcn4 and Ste12 are also sufficient when tethered to an ectopic site to recruit chromatin to the nuclear periphery. For each TF, we have defined the molecular basis of regulated relocalization to the nuclear periphery. Put3- and Cbf1-mediated targeting to nuclear periphery is regulated through local recruitment of Rpd3(L) histone deacetylase complex by transcriptional repressors. Rpd3(L), through its histone deacetylase activity, prevents TF-mediated gene positioning by blocking TF binding. Yeast transcriptional repressors were capable of blocking Put3-mediated recruitment; 11 of these required Rpd3. Thus, it is a general function of transcription repressors to regulate TF-mediated recruitment. However, Ste12 and Gcn4-mediated recruitment is regulated independently of Rpd3(L) and transcriptional repressors. Ste12-mediated recruitment is regulated by phosphorylation of an inhibitor called Dig2, and Gcn4-mediated gene targeting is up-regulated by increasing Gcn4 protein levels. Gcn4-mediated gene targeting genetically requires NPC (Nup2), SAGA (Gcn5 & Spt20), Mediator (Med31), Mex67, however of these only the NPC is directly involved in recruitment of HIS4 to the nuclear periphery. Finally, by iterative deletion from amino and carboxyl termini, a 27 aa Positioning Domain (PD) of Gcn4 was identified. The PD of Gcn4 is sufficient to reposition and cluster chromatin at the nuclear periphery. The ability of transcription factors to mediate recruitment to the NPC and interchromosomal clustering of genes represents a novel function. This ability allows cells to alter the organization of the genome in a directed and regulated manner.

Last modified

• 02/27/2018

Creator

• Carlo Randise-Hinchliff

DOI

• https://doi.org/10.21985/N2JH5J

Subject

• Interdepartmental Biological Sciences (IBiS) Graduate Program

Keyword

• Molecular biology
• Cellular biology

Date created

• 2017-01-01

Resource type

• Dissertation

Rights statement

• In Copyright