TY - JOUR
T1 - Monoubiquitination of survival motor neuron regulates its cellular localization and Cajal body integrity
AU - Han, Ke Jun
AU - Foster, Daniel
AU - Harhaj, Edward W.
AU - Dzieciatkowska, Monika
AU - Hansen, Kirk
AU - Liu, Chang Wei
N1 - Funding Information:
This work was supported by a National Institutes of Health grant to C.-W. L. (grant no. 5RO1NS72397) and aCure SMAgrant to K.-J.H.. We are grateful to Dr DerekW. Abbott (CaseWestern Reserve University) for providing the Itch plasmid, Dr Lydia Matesic (University of South Carolina) for Itch-/- MEFs and Dr Stephen J. Elledge (Harvard Medical School) for providing the pLenti-GPS-GAWvector. We thank members of the Liu lab for insightful discussion and reading of the manuscript. All shRNA constructs were purchased from the Functional Genomics Facility at the University of Colorado Denver (Aurora, Colorado), which is supported by the Cancer Center Support grant (P30CA046934).
Publisher Copyright:
© The Author 2016.
PY - 2016/4/1
Y1 - 2016/4/1
N2 - Low levels of the survival motor neuron (SMN) protein cause spinal muscular atrophy, the leading genetic disorder for infant mortality. SMN is ubiquitously expressed in various cell types and localizes in both the cytoplasm and the nucleus, where it concentrates in two subnuclear structures termed Cajal body (CB) and gems. In addition, SMN can also be detected in the nucleolus of neurons. Mechanisms that control SMN sorting in the cell remain largely unknown. Here, we report that the ubiquitin (Ub) ligase Itch directly interacts with and monoubiquitinates SMN. Monoubiquitination of SMN has a mild effect on promoting proteasomal degradation of SMN. We generated two SMN mutants, SMN(K0), in which all lysines are mutated to arginines and thereby abolishing SMN ubiquitination, and Ub-SMN(K0), in which a single Ub moiety is fused at the N-terminus of SMN(K0) and thereby mimickingSMNmonoubiquitination. Immunostaining assays showed that SMN(K0) mainly localizes in the nucleus, whereas Ub-SMN(K0) localizes in both the cytoplasm and the nucleolus in neuronal SH-SY5Y cells. Interestingly, canonical CB foci and coilin/small nuclear ribonucleoprotein (snRNP) co-localization are significantly impaired in SH-SY5Y cells stably expressing SMN(K0) or Ub-SMN(K0). Thus, our studies discover that Itch monoubiquitinates SMN and monoubiquitination of SMN plays an important role in regulating its cellular localization. Moreover, mislocalization of SMN disrupts CB integrity and likely impairs snRNP maturation.
AB - Low levels of the survival motor neuron (SMN) protein cause spinal muscular atrophy, the leading genetic disorder for infant mortality. SMN is ubiquitously expressed in various cell types and localizes in both the cytoplasm and the nucleus, where it concentrates in two subnuclear structures termed Cajal body (CB) and gems. In addition, SMN can also be detected in the nucleolus of neurons. Mechanisms that control SMN sorting in the cell remain largely unknown. Here, we report that the ubiquitin (Ub) ligase Itch directly interacts with and monoubiquitinates SMN. Monoubiquitination of SMN has a mild effect on promoting proteasomal degradation of SMN. We generated two SMN mutants, SMN(K0), in which all lysines are mutated to arginines and thereby abolishing SMN ubiquitination, and Ub-SMN(K0), in which a single Ub moiety is fused at the N-terminus of SMN(K0) and thereby mimickingSMNmonoubiquitination. Immunostaining assays showed that SMN(K0) mainly localizes in the nucleus, whereas Ub-SMN(K0) localizes in both the cytoplasm and the nucleolus in neuronal SH-SY5Y cells. Interestingly, canonical CB foci and coilin/small nuclear ribonucleoprotein (snRNP) co-localization are significantly impaired in SH-SY5Y cells stably expressing SMN(K0) or Ub-SMN(K0). Thus, our studies discover that Itch monoubiquitinates SMN and monoubiquitination of SMN plays an important role in regulating its cellular localization. Moreover, mislocalization of SMN disrupts CB integrity and likely impairs snRNP maturation.
UR - http://www.scopus.com/inward/record.url?scp=84963719829&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84963719829&partnerID=8YFLogxK
U2 - 10.1093/hmg/ddw021
DO - 10.1093/hmg/ddw021
M3 - Article
C2 - 26908624
AN - SCOPUS:84963719829
SN - 0964-6906
VL - 25
SP - 1392
EP - 1405
JO - Human molecular genetics
JF - Human molecular genetics
IS - 7
M1 - ddw021
ER -