Regulation of stress-inducible phosphoprotein 1 nuclear retention by protein inhibitor of activated STAT PIAS1.
Stress-inducible phosphoprotein 1 (STI1), a cochaperone for Hsp90, has been shown to regulate multiple pathways in astrocytes, but its contributions to cellular stress responses are not fully understood. We show that in response to irradiation-mediated DNA damage stress STI1 accumulates in the nucleus of astrocytes. Also, STI1 haploinsufficiency decreases astrocyte survival after irradiation. Using yeast two-hybrid screenings we identified several nuclear proteins as STI1 interactors. Overexpression of one of these interactors, PIAS1, seems to be specifically involved in STI1 nuclear retention and in directing STI1 and Hsp90 to specific sub-nuclear regions. PIAS1 and STI1 co-immunoprecipitate and PIAS1 can function as an E3 SUMO ligase for STI. Using mass spectrometry we identified five SUMOylation sites in STI1. A STI1 mutant lacking these five sites is not SUMOylated, but still accumulates in the nucleus in response to increased expression of PIAS1, suggesting the possibility that a direct interaction with PIAS1 could be responsible for STI1 nuclear retention. To test this possibility, we mapped the interaction sites between PIAS1 and STI1 using yeast-two hybrid assays and surface plasmon resonance and found that a large domain in the N-terminal region of STI1 interacts with high affinity with amino acids 450-480 of PIAS1. Knockdown of PIAS1 in astrocytes impairs the accumulation of nuclear STI1 in response to irradiation. Moreover, a PIAS1 mutant lacking the STI1 binding site is unable to increase STI1 nuclear retention. Interestingly, in human glioblastoma multiforme PIAS1 expression is increased and we found a significant correlation between increased PIAS1 expression and STI1 nuclear localization. These experiments provide evidence that direct interaction between STI1 and PIAS1 is involved in the accumulation of nuclear STI1. This retention mechanism could facilitate nuclear chaperone activity.
Robarts Research Institute, The University of Western Ontario, London, ON, Canada;
Iaci N
IN
Soares
Fabiana A
FA
Caetano
Jordan
J
Pinder
Bruna Roz
BR
Rodrigues
Flavio H
FH
Beraldo
Valeriy G
VG
Ostapchenko
Chantal
C
Durette
Grace Schenatto
GS
Pereira
Marilene H
MH
Lopes
Nicolle
N
Queiroz-Hazarbassanov
Isabela W
IW
Cunha
Paulo I
PI
Sanematsu
Sergio
S
Suzuki
Luiz F
LF
Bleggi-Torres
Caroline
C
Schild-Poulter
Pierre
P
Thibault
Graham
G
Dellaire
Vilma R
VR
Martins
Vania F
VF
Prado
Marco A M
MA
Prado
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects; D016923:Cell Death / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004249:DNA Damage; D005720:Gamma Rays; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D057895:Haploinsufficiency; D006360:Heat-Shock Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D050828:Protein Inhibitors of Activated STAT / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D060066:Protein Interaction Maps; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological; D058207:Sumoylation; D020798:Two-Hybrid System Techniques
D006360:Heat-Shock Proteins; C494211:Pias1 protein, mouse; D050828:Protein Inhibitors of Activated STAT; D011993:Recombinant Fusion Proteins; C489791:Stip1 protein, mouse