Biomedical subjects

Harinder Singh

Publications and source records attributed to Harinder Singh.

22 records · Page 2Linked to original sources

PubMed2002

PU.1 regulates expression of the interleukin-7 receptor in lymphoid progenitors.

Development of the lymphoid system is dependent on the Ets family transcription factor PU.1. We demonstrate that PU.1(-/-) hematopoietic progenitors fail to express IL-7Ralpha transcripts. Promoter and chromatin crosslinking analyses suggest that PU.1 directly regulates transcription of the IL-7Ralpha gene. Retroviral transduction of IL-7Ralpha into PU.1(-/-) progenitors restores IL-7-dependent proliferation and induces, at low frequency, the generation of pro-B cells undergoing an apparently normal program of differentiation. Although the related factor Spi-B can substitute for PU.1 in early B cell development, it is not required. These results demonstrate that PU.1 functions to regulate early B cell development in part by controlling the expression of the IL-7Ralpha gene.

3T3 Cells↗

PubMed2002

Cooperative and antagonistic interplay between PU.1 and GATA-2 in the specification of myeloid cell fates.

PU.1 and GATA transcription factors appear to antagonize each other's function in the development of distinct lineages of the hematopoietic system. In contrast, we demonstrate that PU.1, like GATA-2, is essential for the generation of mast cells. PU.1-/- hematopoietic progenitors can be propagated in IL-3 and differentiate into mast cells or macrophages upon restoration of PU.1 activity. Using these progenitors and a conditionally activatable PU.1 protein, we show that PU.1 can negatively regulate expression of the GATA-2 gene. In the absence of GATA-2, PU.1 promotes macrophage but not mast cell differentiation. Reexpression of GATA-2 in such progenitors enables the generation of mast cells. We propose a developmental model in which cooperative function or antagonistic crossregulation by PU.1 of GATA-2 promotes distinct myeloid cell fates.

Animals↗

PubMed2002

POU/TBP cooperativity: a mechanism for enhancer action from a distance.

Enhancers when functioning at a distance cannot effectively stimulate transcription from core promoters. We demonstrate that this is due to the inability of enhancer-bound activators to recruit TBP to a distal TATA box. Surprisingly, binding of a transcriptionally inert Oct-1 POU domain near a core promoter enables an enhancer to function from a distance. POU activity neither requires the coactivator OCA-B nor the interaction of TBP with TFIIA. Instead, the POU domain directly facilitates TBP recruitment to the promoter utilizing a bipartite interaction surface. These results establish that an interaction between the DNA binding domain of an activator and TBP can be used to stimulate transcription. Furthermore, they suggest a mechanism for long-range enhancer function in which a TBP complex is preassembled on a promoter via localized recruitment and then acted upon by distal activators.

Animals↗

PubMed2002

Crystal structure of PU.1/IRF-4/DNA ternary complex.

The Ets and IRF transcription factor families contain structurally divergent members, PU.1, Spi-B and IRF-4 (Pip), IRF-8 (ICSBP), respectively, which have evolved to cooperatively assemble on composite DNA elements and regulate gene expression in the immune system. Whereas PU.1 recruits IRF-4 or IRF-8 to DNA, it exhibits an anticooperative interaction with IRF-1 and IRF-2. We report here the structure of the ternary complex formed with the DNA binding domains of PU.1 and IRF-4 on a composite DNA element. The DNA in the complex contorts into an unusual S shape that juxtaposes PU.1 and IRF-4 for selective electrostatic and hydrophobic interactions across the central minor groove. Together, the protein-protein and protein-DNA interactions provide insights into the stereochemical basis of cooperativity and anti-cooperativity between Ets and IRF factors.

Amino Acid Sequence↗