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Hmo1 directs pre-initiation complex assembly to an appropriate site on its target gene promoters by masking a nucleosome-free region.

ABSTRACT: Saccharomyces cerevisiae Hmo1 binds to the promoters of ? 70% of ribosomal protein genes (RPGs) at high occupancy, but is observed at lower occupancy on the remaining RPG promoters. In ?hmo1 cells, the transcription start site (TSS) of the Hmo1-enriched RPS5 promoter shifted upstream, while the TSS of the Hmo1-limited RPL10 promoter did not shift. Analyses of chimeric RPS5/RPL10 promoters revealed a region between the RPS5 upstream activating sequence (UAS) and core promoter, termed the intervening region (IVR), responsible for strong Hmo1 binding and an upstream TSS shift in ?hmo1 cells. Chromatin immunoprecipitation analyses showed that the RPS5-IVR resides within a nucleosome-free region and that pre-initiation complex (PIC) assembly occurs at a site between the IVR and a nucleosome overlapping the TSS (+1 nucleosome). The PIC assembly site was shifted upstream in ?hmo1 cells on this promoter, indicating that Hmo1 normally masks the RPS5-IVR to prevent PIC assembly at inappropriate site(s). This novel mechanism ensures accurate transcriptional initiation by delineating the 5'- and 3'-boundaries of the PIC assembly zone.

SUBMITTER: Kasahara K

PROVIDER: S-EPMC3105432 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Hmo1 directs pre-initiation complex assembly to an appropriate site on its target gene promoters by masking a nucleosome-free region.

Kasahara Koji K Ohyama Yoshifumi Y Kokubo Tetsuro T

Nucleic acids research 20110202 10

Saccharomyces cerevisiae Hmo1 binds to the promoters of ∼ 70% of ribosomal protein genes (RPGs) at high occupancy, but is observed at lower occupancy on the remaining RPG promoters. In Δhmo1 cells, the transcription start site (TSS) of the Hmo1-enriched RPS5 promoter shifted upstream, while the TSS of the Hmo1-limited RPL10 promoter did not shift. Analyses of chimeric RPS5/RPL10 promoters revealed a region between the RPS5 upstream activating sequence (UAS) and core promoter, termed the interven ...[more]

PMID: 21288884

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Project description:Myeloid translocation genes (MTGs) are transcriptional corepressors originally identified in acute myelogenous leukemia that have recently been linked to epithelial malignancy with non-synonymous mutations identified in both MTG8 and MTG16 in colon, breast, and lung carcinoma in addition to functioning as negative regulators of WNT and Notch signaling. A yeast two-hybrid approach was used to discover novel MTG binding partners. This screen identified the Zinc fingers, C2H2 and BTB domain containing (ZBTB) family members ZBTB4 and ZBTB38 as MTG16 interacting proteins. ZBTB4 is downregulated in breast cancer and modulates p53 responses. Because ZBTB33 (Kaiso), like MTG16, modulates Wnt signaling at the level of TCF4, and its deletion suppresses intestinal tumorigenesis in the Apc(Min) mouse, we determined that Kaiso also interacted with MTG16 to modulate transcription. The zinc finger domains of Kaiso as well as ZBTB4 and ZBTB38 bound MTG16 and the association with Kaiso was confirmed using co-immunoprecipitation. MTG family members were required to efficiently repress both a heterologous reporter construct containing Kaiso binding sites (4×KBS) and the known Kaiso target, Matrix metalloproteinase-7 (MMP-7/Matrilysin). Moreover, chromatin immunoprecipitation studies placed MTG16 in a complex occupying the Kaiso binding site on the MMP-7 promoter. The presence of MTG16 in this complex, and its contributions to transcriptional repression both required Kaiso binding to its binding site on DNA, establishing MTG16-Kaiso binding as functionally relevant in Kaiso-dependent transcriptional repression. Examination of a large multi-stage CRC expression array dataset revealed patterns of Kaiso, MTG16, and MMP-7 expression supporting the hypothesis that loss of either Kaiso or MTG16 can de-regulate a target promoter such as that of MMP-7. These findings provide new insights into the mechanisms of transcriptional control by ZBTB family members and broaden the scope of co-repressor functions for the MTG family, suggesting coordinate regulation of transcription by Kaiso/MTG complexes in cancer.

Dataset Information

Hmo1 directs pre-initiation complex assembly to an appropriate site on its target gene promoters by masking a nucleosome-free region.

Publications

Hmo1 directs pre-initiation complex assembly to an appropriate site on its target gene promoters by masking a nucleosome-free region.

Similar Datasets

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