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THE ROLE OF CHROMATIN REMODELING IN RB-MEDIATED CELL CYCLE ARREST

STROBECK, MATTHEW WILLIAM
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1014728057

Abstract Details

2002, PhD, University of Cincinnati, Medicine : Cell and Molecular Biology.
The anti-proliferative action of the retinoblastoma tumor suppressor protein, RB, is disrupted in the majority of human cancers by multiple mechanisms including: i) viral oncoprotein binding, ii) deregulated RB phosphorylation, and iii) direct mutation of the RB gene. Here we report disruption of RB signaling in tumor cells through the loss of two critical cooperating factors, and the potential impact of these events on tumor formation. Phosphorylation/inactivation of RB is typically required for cell cycle progression. However, we identified a tumor cell line, C33A, which progresses through the cell cycle in the presence of a constitutively active allele of RB (PSM-RB). Utilizing somatic cell fusions we determined that in C33A cells, RB lacks a factor required for signaling to Cyclin A, and identified this factor as BRG-1, a SWI/SNF chromatin remodeling protein. Since BRG-1 was suggested to interact and potentially cooperate with RB, we hypothesized that BRG-1 loss may confer RB-resistance. Using BRG-1 as a candidate marker we identified two other BRG-1 deficient tumor cell lines, SW13 and PANC-1 that are insensitive to RB signaling. This deficiency in RB-mediated transcriptional repression and cell cycle inhibition was rescued through the ectopic co-expression of BRG-1, and specific BRG-1 abrogation resulted in loss of RB activity. These results identify a mechanism by which RB activity is lost in human tumor cells, and were the first to demonstrate that loss of RB cooperative proteins have biological consequence. Since BRG-1 loss is tantamount to RB loss, we wanted to identify a marker for BRG-1 activity. After screening for BRG-1 regulated targets, we identified CD44, a membrane glycoprotein involved in cell adhesion and metastasis, as a potential marker. Re-introduction of BRG-1 into C33A or SW13 cells restored CD44 expression, suggesting that BRG-1 is required for maintaining basal CD44 levels. Given the importance of BRG-1 in RB and CD44 function/expression, we assessed the behavior of cells harboring discrete BRG-1 alleles for these signaling pathways. While these pathways remained intact in several BRG-1 mutant tumor cells, our studies revealed that tumor lines defective for both BRG-1 and Brm, a SWI/SNF homologue, were resistant to RB and failed to express CD44. Moreover, we showed that reintroduction of either BRG-1 or Brm restores signaling to both effector pathways, revealing a compensatory role of Brm with BRG-1. Thus, these findings reveal a novel mechanism through which tumor cells evade anti-proliferative signals, and provide insight into how RB-signaling is mediated.
Dr. Erik Knudsen (Advisor)
169 p.
retinoblastoma; cell cycle; Cyclin A; BRG-1; SWI/SNF

Recommended Citations

Citations

  • STROBECK, M. W. (2002). THE ROLE OF CHROMATIN REMODELING IN RB-MEDIATED CELL CYCLE ARREST [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1014728057

    APA Style (7th edition)

  • STROBECK, MATTHEW. THE ROLE OF CHROMATIN REMODELING IN RB-MEDIATED CELL CYCLE ARREST. 2002. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1014728057.

    MLA Style (8th edition)

  • STROBECK, MATTHEW. "THE ROLE OF CHROMATIN REMODELING IN RB-MEDIATED CELL CYCLE ARREST." Doctoral dissertation, University of Cincinnati, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1014728057

    Chicago Manual of Style (17th edition)

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© 2002, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.