Department of Biochemistry Box 357350 University of Washington Seattle, WA 98195
 



 
 
 
      

Brian Kennedy              


Associate Professor of Biochemistry

PhD 1996, MIT
BA 1989, Northwestern University

206.685.0111 V
206.685.1792 F
bkenn@u.washington.edu





Research

Research in the lab is progressing along two overlapping tracts. In one project, we use a variety of molecular, biochemical and cell biological approaches to understand how the mammalian nucleus is organized. Of primary interest is the spatial control of DNA synthesis and the function of A-type nuclear lamins. A second project is focused under understanding the molecular underpinnings of eukaryotic aging. A number of aging genes have been identified, including A-type nuclear lamins, in a variety of aging model systems. We are addressing both the mechanisms by which these aging genes influence the rate of aging and the level of conservation of aging pathways across eukaryotes.

A-type Nuclear Lamins

Lamins are intermediate filament proteins and core structural components of the mammalian nucleus. Unlike B-type lamins, which are expressed universally and thought to be required for cell viability, A-type lamins expression is largely restricted to differentiating tissues. Mutations in LMNA, encoding all A-type lamins arising through differential splicing, have been associated with a wide spectrum of human diseases including types of muscular dystrophy, lipodystrophy and progeria. By understanding the molecular basis of these diseases, we hope to learn important insights into nuclear organization and more specifically the links between nuclear lamins and chromatin organization.

Two models have been proposed to explain A-type lamin-linked diseases. In the structural model, it has been speculated that A-type lamins are required for nuclear and/or cellular integrity. This may be particularly important in muscle tissue, where cells are routinely exposed to torsional stress. In contrast, a transcriptional model has been proposed whereby A-type lamins help establish or maintain tissue-specific gene expression programs. We have used in vitro systems to look at muscle and fat cell differentiation under conditions where A-type lamin activity has been reduced or eliminated. Myoblasts lacking A-type lamins exhibit reduced MyoD levels and are severely compromised for differentiation into myotubes. We are currently studying the molecular nature of this defect. These findings point to a role for A-type lamins in controlling muscle-specific gene expression programs. However, mice lacking lamins develop severe muscular dystrophy, and are much more strongly affected than mice lacking MyoD. Therefore we speculate that with regard to muscular dystrophy, both aforementioned models for disease may be correct. Muscle cells from mammals lacking A-type lamin function may be more prone to degeneration due to loss of cell integrity under torsional stress and less able to regenerate replacement muscle due to altered tissue-specific gene expression programs.





Spatial Control of DNA Synthesis

Recently, we have shown that patterns of DNA synthesis in the mammalian nucleus are highly dynamic. Replication occurs at different subnuclear sites at different positions in the cell cycle. Moreover, replication patterns are altered by cell immortalization and by changes in proliferation rate. Our long-term goals are to understand the manner by which DNA synthesis is compartmentalized in the nucleus and the reasons why this process is highly regulated. We propose that different replication foci may contain different chromatin remodeling factors; therefore, changing the location of replication of a chromosomal region may in turn alter expression states of genes within that region.



Molecular Biology of Aging

We have initiated genome-wide screens to identify yeast genes that regulate aging. Having identified these genes, we are attempting to determine the level of conservation of aging pathways among different eukaryotic aging model systems (worms and mice) by testing the longevity phenotypes of their orthologs. These large scale studies are made possible by a grant from the Ellison Medical Foundation and in collaboration with a number of scientists at the University of Washington, including Stan Fields, Matt Kaeberlein, Warren Ladiges, George Martin, Peter Rabinovitch, and Jim Thomas. See http://www.pathology.washington.edu/research/bioage/ellison/ for more information.

We also seek to identify the molecular pathways that coordinate yeast longevity. Ultimately we hope to understand all major aging pathways in yeast and to determine whether they are acting similarly in mammals. Of particular interest are the pathways which are required for life span extension by calorie restriction. Calorie restriction (CR) is the only intervention known to increase life-span in yeast, worms, flies, and mammals, but the molecular mechanism for this phenomenon remains mysterious. By understanding calorie restriction in yeast, we hope to develop hypothesis that can be tested in multicellular eukaryotes including mammals.

Selected Publications

Kaeberlein M, Powers RW III, Steffen KK, Westman EA, Hu D, Dang N, Kerr EO, Kirkland KT, Fields S, Kennedy BK (2005). Regulation of yeast replicative life span by TOR and Sch9 in response to nutrients. Science 310, 1193-6.

Kaeberlein M, Hu D, Kerr EO, Tsuchiya M, Westman EA, Dang N, Fields S, Kennedy BK (2005). Increased life span due to calorie restriction in respiratory-deficient yeast. PLoS Genet. 1, e69 [epub ahead of print].

Kennedy BK (2005). The enigmatic role of Sir2 in aging. Cell 123, 548-50.

Kudlow BA, Jameson SA, and Kennedy BK. HIV protease inhibitors block adipocyte differentiation independently of lamin A/C. AIDS 19: 1565-1573.

Barbie DA, Conlan LA, and Kennedy BK. 2005. Nuclear tumor suppressors in space and time. Trends Cell Biol. 15: 378-385.

Kaeberlein M, McDonagh T, Heltweg B, Hixon J, Westman EA, Caldwell S, Napper A, Curtis R, DiStefano PS, Fields S, Bedalov A, and Kennedy BK (2005) Substrate specific activation of sirtuins by resveratrol. J. Biol. Chem. 280:17039-17045.

Smith ED, Kudlow BA, Frock RL and Kennedy BK (2005) A-type nuclear lamins, progerias and other degenerative disorders. Mech. Ageing Dev. 126: 447-460.

Kaeberlein, M, Kirkland KT, Fields S, and Kennedy BK (2005) Genes determining yeast replicative life span in a long-lived genetic background. Mech. Ageing Dev. 126: 491-504.

Huang S, Kennedy BK, and Oshima, J. 2005. LMNA mutations in progeroid syndromes. Novartis Found. Symp. 264:197-202.

Kaeberlein M and Kennedy BK (2005) Large-scale identification in yeast of conserved ageing genes. Mech. Ageing Dev. 126: 17-21.

Johnson BR, Nitta R, Frock RL, Mounkes L, Barbie DA, Stewart C, Harlow E, and Kennedy BK (2004) A-type lamins regulate retinoblastoma protein function by promoting subnuclear localization and preventing proteasomal degradation. Proc. Natl. Acad. Sci., USA 101: 9677-9682.

Kaeberlein M, Kirkland KT, Fields S, and Kennedy BK (2004) Sir2-independent life span extension by calorie restriction in yeast. PLoS Biology 2: 1381-1387.

Barbie DA, Kudlow BA, Frock R, Zhao J, Johnson BR, Dyson N, Harlow E and Kennedy BK (2004) Nuclear reorganization of mammalian DNA synthesis prior to cell cycle exit. Mol. Cell. Biol. 24: 595-607.

Chen L, Lee L, Kudlow BA, Dos Santos HG, Sletvold O, Shafeghati Y, Botha EG, Garg A, Hanson NB, Martin GM, Mian IS, Kennedy BK, and Oshima, J (2003) LMNA mutations in atypical Werner's syndrome. Lancet 362: 440-445.

Kennedy BK (2002) Mammalian transcription factors in yeast: strangers in a familiar land. Nat. Rev. Mol. Cell Biol. 3: 41-49.

Kennedy BK, Barbie DA, Classon M, Dyson N, and Harlow E. 2000. Nuclear organization of DNA replication in primary mammalian cells. Genes Dev. 14: 2855-68.