Identification and functional analysis of SKA2 interaction with the glucocorticoid receptor.
Glucocorticoid (GC) receptors (GRs) have profound anti-survival effects on human small cell lung cancer (SCLC). To explore the basis of these effects, protein partners for GRs were sought using a yeast two-hybrid screen. We discovered a novel gene, FAM33A, subsequently identified as a SKA1 partner and involved in mitosis, and so renamed Ska2. We produced an anti-peptide antibody that specifically recognized full-length human SKA2 to measure expression in human cell lines and tissues. There was a wide variation in expression across multiple cell lines, but none was detected in the liver cell line HepG2. A xenograft model of human SCLC had intense staining and archival tissue revealed SKA2 in several human lung and breast tumours. SKA2 was found in the cytoplasm, where it co-localized with GR, but nuclear expression of SKA2 was seen in breast tumours. SKA2 overexpression increased GC transactivation in HepG2 cells while SKA2 knockdown in A549 human lung epithelial cells decreased transactivation and prevented dexamethasone inhibition of proliferation. GC treatment decreased SKA2 protein levels in A549 cells, as did Staurosporine, phorbol ester and trichostatin A; all agents that inhibit cell proliferation. Overexpression of SKA2 potentiated the proliferative response to IGF-I exposure, and knockdown with shRNA caused cells to arrest in mitosis. SKA2 has recently been identified in HeLa S3 cells as part of a complex, which is critical for spindle checkpoint silencing and exit from mitosis. Our new data show involvement in cell proliferation and GC signalling, with implications for understanding how GCs impact on cell fate.
Rice
Lisa
L
Faculty of Medical and Human Sciences, School of Medicine, University of Manchester, Manchester M13 9PT, UK.
Waters
Charlotte E
CE
Eccles
Jennifer
J
Garside
Helen
H
Sommer
Paula
P
Kay
Paul
P
Blackhall
Fiona H
FH
Zeef
Leo
L
Telfer
Brian
B
Stratford
Ian
I
Clarke
Rob
R
Singh
Dave
D
Stevens
Adam
A
White
Anne
A
Ray
David W
DW
D041721:3T3-L1 Cells; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008175:Lung Neoplasms / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics / Q000502:physiology; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques
D002868:Chromosomal Proteins, Non-Histone; D034741:RNA, Small Interfering; D011965:Receptors, Glucocorticoid; C516428:SKA2 protein, human