The human La (SS-B) autoantigen interacts with DDX15/hPrp43, a putative DEAH-box RNA helicase.
The human La (SS-B) autoantigen is an abundantly expressed putative RNA chaperone, functioning in various intracellular processes involving RNA. To further explore the molecular mechanisms by which La functions in these processes, we performed large-scale immunoprecipitations of La from HeLa S100 extracts using the anti-La monoclonal antibody SW5. La-associated proteins were subsequently identified by sequence analysis. This approach allowed the identification of DDX15 as a protein interacting with La. DDX15, the human ortholog of yeast Prp43, is a member of the superfamily of DEAH-box RNA helicases that appeared to interact with La both in vivo and in vitro. The region needed for the interaction with La partly overlaps the DEAH-box domain of DDX15. Immunofluorescence data indicated that endogenous DDX15 accumulates in U snRNP containing nuclear speckles in HEp-2 cells. Surprisingly DDX15 also accumulates in the nucleoli of HEp-2 cells. Moreover, DDX15 and La seem to colocalize in the nucleoli. Regions of DDX15 involved in nuclear, nuclear speckle, and nucleolar localization are located within the N- and C-terminal regions flanking the DEAH-box. RNA coprecipitation experiments indicated that DDX15 is associated with spliceosomal U small nuclear RNAs in HeLa cell extracts. The possible functional implications of the interaction between La and DDX15 are discussed.
Fouraux
Michael A
MA
Department of Biochemistry, Nijmegen Center for Molecular Life Sciences, University of Nijmegen, Nijmegen, The Netherlands.
Kolkman
Marloes J M
MJ
Van der Heijden
Annemarie
A
De Jong
Arjan S
AS
Van Venrooij
Walther J
WJ
Pruijn
Ger J M
GJ
D000595:Amino Acid Sequence; D001324:Autoantigens / Q000276:immunology / Q000378:metabolism*; D001665:Binding Sites; D002466:Cell Nucleolus / Q000378:metabolism*; D053487:DEAD-box RNA Helicases; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000276:immunology; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing; D012342:RNA, Small Nuclear / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012261:Ribonucleoproteins / Q000276:immunology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014759:Viral Envelope Proteins / Q000276:immunology; D000097585:SS-B Antigen
D001324:Autoantigens; D053487:DEAD-box RNA Helicases; D008562:Membrane Glycoproteins; D020365:RNA Helicases; D012342:RNA, Small Nuclear; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins; D014759:Viral Envelope Proteins; D000097585:SS-B Antigen; C028391:G protein, vesicular stomatitis virus; C405483:U1 small nuclear RNA; C109034:PRP43 protein, S cerevisiae