All ETDs from UAB

Advisory Committee Chair

Zhixin Zhang

Advisory Committee Members

Louis B Justement

Christopher A Klug

Peter B Burrows

Chander Raman

Document Type

Dissertation

Date of Award

2008

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

B lineage cells are major players in the adaptive immune system. Pax5 is essential for B lineage cell development and function. Pax5 controls B lineage cell developmental progression by regulating expression of many B lineage specific genes and the B lineage specific VH to DJH recombination; and the meantime, Pax5 also represses the transcription of lineage- and developmental stage- inappropriate genes to restrict the B lineage developmental pathway. It is not clear how Pax5-mediated function can be regulated to fulfill its role in different biological reactions. In this dissertation, we focused on the study of the molecular regulation of Pax5-mediated functions. In part I, our results showed that Pax5-mediated transcriptional activation can be dramatically elevated by overexpression of histone acetyltransferase p300. We found that p300 directly interacts with Pax5 and acetylates multiple lysine residues within the Nterminal regions of the Pax5 protein. Mutation of the lysine 67, 87, 89, 103, or 142 residues into alanine diminished p300 mediated enhancement of Pax5 function in activation of Luc-Cd19 reporter gene expression. Moreover, mutations of lysine 67, 87/89 in Pax5 impaired Pax5-mediated activation of endogenous Pax5 target genes in Pax5-/- mouse pro B cells, indicating that acetylation of Pax5 provides an important regulation for Pax5-mediated biological functions during B lineage cell development. In part II, to understand how Pax5 mediates global effects during B cell development, we analyzed the nuclear sub-localization of Pax5. It has long been hypothesized that v transcription in cells occurs on the discrete loci associated with the nuclear matrix inside the nucleus. We found that most endogenous Pax5 in human or mouse B lineage cells associates with the nuclear matrix. In addition, Pax5 co-localizes with the basal transcriptional machinery. We found that the partial homeodomain and its flanking regions contain signals to target Pax5 to the nuclear matrix. Deletion of the partial homeodomain of Pax5 compromises Pax5-mediated transcriptional activation of many target genes. These results indicate that the association with the nuclear matrix is essential for Pax5 to fully activate endogenous B lineage specific genes. Taken together, the results presented in this dissertation uncovered two novel mechanisms that regulate Pax5-mediated transcription function.

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