Direct binding of nuclear membrane protein MAN1 to emerin in vitro and two modes of binding to barrier-to-autointegration factor.
MAN1 is a vertebrate nuclear inner membrane protein that inhibits Smad signaling downstream of transforming growth factor beta. MAN1 has an exposed LEM domain-containing N-terminal region ("MAN1-N"), two transmembrane domains, and an exposed C-terminal domain ("MAN1-C"). Many regions of human MAN1 are homologous to emerin, a LEM domain nuclear protein, loss of which causes Emery-Dreifuss muscular dystrophy (EDMD). To test the hypothesis that MAN1 function might overlap with emerin, we tested different polypeptide fragments of MAN1 for binding to selected partners of emerin. Our findings support this hypothesis. Blot overlay assays and co-immunoprecipitation studies showed that MAN1-C binds the transcription regulators GCL, Btf, and barrier-to-autointegration factor (BAF). BAF binding to this region, which has no LEM domain, was notable. Sequence alignments identified a potential BAF-binding motif, characterized by the conserved residues Ser-Arg-Val, in MAN1-C and two other BAF-binding proteins. The other region, MAN1-N, bound directly to BAF, lamin A, and lamin B1, supporting functional overlap with emerin. Unexpectedly, three independent assays showed that MAN1-N also bound directly to emerin. Proposed MAN1-emerin complexes are discussed in the context of EDMD disease mechanisms and potential in vivo functions.
Mansharamani
Malini
M
Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Wilson
Katherine L
KL
D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013946:Thymopoietins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
C501959:BANF1 protein, human; C119386:BCLAF1 protein, human; D004268:DNA-Binding Proteins; C501308:GMCL1 protein, human; C405329:LEMD3 protein, human; D008565:Membrane Proteins; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D012097:Repressor Proteins; D013946:Thymopoietins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C092710:emerin