A Role for the Transcriptional Coactivator PRC1 in Mitochondrial Biogenesis During Erythroid Development.

Abstract 3642

Poster Board III-578

Red cell development requires unparalleled mitochondrial metabolic and biosynthetic capacities to support hemoglobin formation. In addition to meeting the energetic requirements of the erythroblast and reticulocyte, mitochondria are the site of multiple steps in heme biosynthesis and are essential for iron utilization. As such, perturbation of mitochondrial function in hematopoietic cells appears to differentially affect red cell development. For instance, we show that the drug chloramphenicol (an inhibitor of mitochondrial protein synthesis) preferentially inhibits erythroid colony formation with relatively little effect on other types of myeloid progenitors. Similarly, we show that knockout of the mitochondrial superoxide dismutase (Sod2) preferentially inhibits BFU-E, CFU-E and GEMM colonies. Clinically, several mutations in mitochondrial DNA or in nuclear encoded mitochondria-localized proteins preferentially disrupt erythroid development resulting in sideroblastic anemia. In order to better understand regulation of mitochondrial activity during red cell development/differentiation, we have investigated expression of transcription factors and coactivators implicated as regulators of mitochondrial biogenesis in other tissues including PGC-1 α and β, ERR proteins, NRF 1 and NRF 2 in normal and Sod2 deficient murine erythroblasts. Microarray and qPCR data suggest that neither of the classic transcriptional coactivators PGC-1 α or β are expressed at appreciable levels in erythroblasts. However, a PGC-1 related coactivator, PRC1 is detectable at both the transcript and protein level in developing erythroid cells. In the Sod2 deficiency model, one of the most prominent transcriptional changes we have observed in erythroblasts is a broad down regulation of expression of nuclear encoded mitochondria localized protein transcripts including multiple components of the electron transport chain, TCA cycle enzymes and mitochondrial ribosomal proteins. We show that PRC1 expression is down regulated in Sod2 deficient cells—suggesting that this coactivator plays a key role in mitochondrial biogenesis during erythroid development. Further, using the MEL cell line, we show that PRC1 expression is turned on following induction of differentiation with DMSO. These results identify PRC1 as a novel, and perhaps exclusive regulator of mitochondrial biogenesis during erythroid development. A better understanding of regulation of PRC1 expression and identification of transcriptional targets of PRC1 during erythroid development will improve our understanding of how perturbations in mitochondrial physiology affect the red cell compartment.