Abstract

Emerin is a nuclear membrane protein that bines lamina filaments. Emerin mutations cause Emery-Dreifuss muscular dystrophy, affecting heart, skeletal muscle, and tendons. Emerin belongs to the conserved LEM-domain family of nuclear proteins. The LEM-domain of emerin binds BAF (barrier to autointegration factor), a conserved chromatin protein of unknown function. We propose that LEM proteins structurally link chromatin (via BAF) to the lamina, and also bind partners that mediate DNA replication or transcriptional repression. We propose to determine the essential function of three conserved LEM proteins in C.elegans: emerin, MAN1 and lem-3. In C. elelgans, all or most cells express emerin and MAN1, but the RNAi-induced loss of emerin or MAN1 has no phenotype. However, loss of both proteins is lethal in embryos. Thus, emerin and MAN1 have essential function(s). We will test the hypothesis that all three LEM proteins bind directly to BAF and lamin, and use site-directed mutagenesis to map their binding regions. We will use RNAi to deplete each LEM protein, and pairs of LEM proteins to test for overlapping and cell-type-specific functions in vivo. By identifying and characterizing new binding partners for emerin, MAN1 and lem- 3, we will test our hypothesis that LEM proteins are directly involved in replication, transcription, or lamin dynamics. We will determine if mutant LEM proteins, whose binding activities are defined in vitro, can rescue lethality of emerin: MAN1 (RNAi) embryos. WE will screen for mutations that are synthetically lethal in an emerin null or MAN1 null background, to identify proteins that mediate the essential functions of emerin and MAN1. This work will be the first genetic analysis of the nuclear lamina. Our work will yield basic knowledge about the functions of LEM proteins, and their interactions with lamins and BAF. This work can be extended to humans to predict the molecular mechanisms of heart disease and muscular dystrophy caused by loss of emerin.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM064535-04
Application #
6891432
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Shapiro, Bert I
Project Start
2002-05-01
Project End
2007-04-30
Budget Start
2005-05-01
Budget End
2007-04-30
Support Year
4
Fiscal Year
2005
Total Cost
$267,506
Indirect Cost

  Institution

Name
Johns Hopkins University
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218

  Publications

Zastrow, Michael S; Flaherty, Denise B; Benian, Guy M et al. (2006) Nuclear titin interacts with A- and B-type lamins in vitro and in vivo. J Cell Sci 119:239-49
Mansharamani, Malini; Wilson, Katherine L (2005) Direct binding of nuclear membrane protein MAN1 to emerin in vitro and two modes of binding to barrier-to-autointegration factor. J Biol Chem 280:13863-70
Margalit, Ayelet; Segura-Totten, Miriam; Gruenbaum, Yosef et al. (2005) Barrier-to-autointegration factor is required to segregate and enclose chromosomes within the nuclear envelope and assemble the nuclear lamina. Proc Natl Acad Sci U S A 102:3290-5
Margalit, Ayelet; Liu, Jun; Fridkin, Alexandra et al. (2005) A lamin-dependent pathway that regulates nuclear organization, cell cycle progression and germ cell development. Novartis Found Symp 264:231-40; discussion 240-5
Fridkin, Alexandra; Karabinos, Anton; Gruenbaum, Yosef (2004) Intermediate filaments in Caenorhabditis elegans. Methods Cell Biol 78:703-18
Fridkin, Alexandra; Mills, Erez; Margalit, Ayelet et al. (2004) Matefin, a Caenorhabditis elegans germ line-specific SUN-domain nuclear membrane protein, is essential for early embryonic and germ cell development. Proc Natl Acad Sci U S A 101:6987-92
Liu, Jun; Lee, Kenneth K; Segura-Totten, Miriam et al. (2003) MAN1 and emerin have overlapping function(s) essential for chromosome segregation and cell division in Caenorhabditis elegans. Proc Natl Acad Sci U S A 100:4598-603
Mattout-Drubezki, A; Gruenbaum, Y (2003) Dynamic interactions of nuclear lamina proteins with chromatin and transcriptional machinery. Cell Mol Life Sci 60:2053-63
Cohen, Merav; Feinstein, Naomi; Wilson, Katherine L et al. (2003) Nuclear pore protein gp210 is essential for viability in HeLa cells and Caenorhabditis elegans. Mol Biol Cell 14:4230-7
Holaska, James M; Lee, Kenneth K; Kowalski, Amy K et al. (2003) Transcriptional repressor germ cell-less (GCL) and barrier to autointegration factor (BAF) compete for binding to emerin in vitro. J Biol Chem 278:6969-75

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