title: Nuclear role of WASp in gene transcription is uncoupled from its ARP2/3-dependent cytoplasmic role in actin polymerization.
abstract: Defects in Wiskott-Aldrich Syndrome protein (WASp) underlie development of WAS, an X-linked immunodeficiency and autoimmunity disorder of childhood. Nucleation-promoting factors (NPFs) of the WASp family generate F-actin in the cytosol via the VCA (verprolin-homology, cofilin-homology, and acidic) domain and support RNA polymerase II-dependent transcription in the nucleus. Whether nuclear-WASp requires the integration of its actin-related protein (ARP)2/3-dependent cytoplasmic function to reprogram gene transcription, however, remains unresolved. Using the model of human TH cell differentiation, we find that WASp has a functional nuclear localizing and nuclear exit sequences, and accordingly, its effects on transcription are controlled mainly at the level of its nuclear entry and exit via the nuclear pore. Human WASp does not use its VCA-dependent, ARP2/3-driven, cytoplasmic effector mechanisms to support histone H3K4 methyltransferase activity in the nucleus of TH1-skewed cells. Accordingly, an isolated deficiency of nuclear-WASp is sufficient to impair the transcriptional reprogramming of TBX21 and IFNG promoters in TH1-skewed cells, whereas an isolated deficiency of cytosolic-WASp does not impair this process. In contrast, nuclear presence of WASp in TH2-skewed cells is small, and its loss does not impair transcriptional reprogramming of GATA3 and IL4 promoters. Our study unveils an ARP2/3:VCA-independent function of nuclear-WASp in TH1 gene activation that is uncoupled from its cytoplasmic role in actin polymerization.
authors.affiliation: Division of Pediatric Hematology-Oncology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15213;
authors.forename: Sanjoy
authors.initials: S
authors.lastname: Sadhukhan
authors.affiliation: Division of Pediatric Hematology-Oncology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15213; Division of Pediatric Hematology-Oncology, University of Iowa Children's Hospital, Iowa City, IA 52242; and.
authors.forename: Koustav
authors.initials: K
authors.lastname: Sarkar
authors.affiliation: Division of Pediatric Hematology-Oncology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15213;
authors.forename: Matthew
authors.initials: M
authors.lastname: Taylor
authors.affiliation: Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Fabio
authors.initials: F
authors.lastname: Candotti
authors.affiliation: Division of Pediatric Hematology-Oncology, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15213; Division of Pediatric Hematology-Oncology, University of Iowa Children's Hospital, Iowa City, IA 52242; and yatin-vyas@uiowa.edu.
authors.forename: Yatin M
authors.initials: YM
authors.lastname: Vyas
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000235:genetics / Q000276:immunology*; D000199:Actins / Q000235:genetics / Q000276:immunology*; D002467:Cell Nucleus / Q000235:genetics / Q000276:immunology*; D050990:GATA3 Transcription Factor / Q000235:genetics / Q000276:immunology; D006367:HeLa Cells; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000276:immunology; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics / Q000276:immunology; D015847:Interleukin-4 / Q000235:genetics / Q000276:immunology; D019169:Jurkat Cells; D020825:T-Box Domain Proteins / Q000235:genetics / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology*; D014158:Transcription, Genetic / Q000235:genetics / Q000276:immunology*; D051316:Wiskott-Aldrich Syndrome Protein / Q000235:genetics / Q000276:immunology*; D000098815:T-bet Transcription Factor
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D050990:GATA3 Transcription Factor; C494749:GATA3 protein, human; C573415:IFNG protein, human; C508598:IL4 protein, human; D020825:T-Box Domain Proteins; D000098815:T-bet Transcription Factor; C495767:WAS protein, human; D051316:Wiskott-Aldrich Syndrome Protein; D015847:Interleukin-4; D007371:Interferon-gamma; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase