Increased cytoplasmic levels of CIS, SOCS1, SOCS2, or SOCS3 are required for nuclear translocation.
We investigated the cellular localization of ectopically-expressed CIS, SOCS1, SOCS2 and SOCS3 proteins. We found that SOCS proteins localize to the nucleus where they reduce Stat3 proteins and that the presence of proteasome inhibitors increased SOCS nuclear localization. Our results indicate that increased nuclear localization resulted from increased levels of SOCS proteins in the cytoplasm. Finally, we demonstrate that the same effect occurs with endogenously-expressed SOCS proteins. These observations suggest that increased cytoplasmic levels of proteins in the SOCS family are regulated through nuclear translocation.
Lee
Kyeong-Hee
KH
Research Institute, National Cancer Center, 809 Madu 1-dong, Ilsan-gu, Goyang-si, Gyeonggi-do, Republic of Korea.
Moon
Kyeong-Jin
KJ
Kim
Hyung Sik
HS
Yoo
Byong Chul
BC
Park
Seoyoung
S
Lee
Ho
H
Kwon
Soim
S
Lee
Eun Sook
ES
Yoon
Sungpil
S
D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000378:metabolism*
D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D046988:Proteasome Endopeptidase Complex; D061988:Proteasome Inhibitors; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C108944:SOCS1 protein, human; C106643:SOCS2 protein, human; C106644:SOCS3 protein, human; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde