Multiple myeloma–associated chromosomal translocation activates orphan snoRNA ACA11 to suppress oxidative stress
Liang Chu, Mack Y. Su, Leonard B. Maggi Jr., Lan Lu, Chelsea Mullins, Seth Crosby, Gaofeng Huang, Wee Joo Chng, Ravi Vij, Michael H. Tomasson
Liang Chu, Mack Y. Su, Leonard B. Maggi Jr., Lan Lu, Chelsea Mullins, Seth Crosby, Gaofeng Huang, Wee Joo Chng, Ravi Vij, Michael H. Tomasson
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Research Article

Multiple myeloma–associated chromosomal translocation activates orphan snoRNA ACA11 to suppress oxidative stress

Abstract

The histone methyltransferase WHSC1 (also known as MMSET) is overexpressed in multiple myeloma (MM) as a result of the t(4;14) chromosomal translocation and in a broad variety of other cancers by unclear mechanisms. Overexpression of WHSC1 did not transform wild-type or tumor-prone primary hematopoietic cells. We found that ACA11, an orphan box H/ACA class small nucleolar RNA (snoRNA) encoded within an intron of WHSC1, was highly expressed in t(4;14)-positive MM and other cancers. ACA11 localized to nucleoli and bound what we believe to be a novel small nuclear ribonucleoprotein (snRNP) complex composed of several proteins involved in postsplicing intron complexes. RNA targets of this uncharacterized snRNP included snoRNA intermediates hosted within ribosomal protein (RP) genes, and an RP gene signature was strongly associated with t(4;14) in patients with MM. Expression of ACA11 was sufficient to downregulate RP genes and other snoRNAs implicated in the control of oxidative stress. ACA11 suppressed oxidative stress, afforded resistance to chemotherapy, and increased the proliferation of MM cells, demonstrating that ACA11 is a critical target of the t(4;14) translocation in MM and suggesting an oncogenic role in other cancers as well.

Authors

Liang Chu, Mack Y. Su, Leonard B. Maggi Jr., Lan Lu, Chelsea Mullins, Seth Crosby, Gaofeng Huang, Wee Joo Chng, Ravi Vij, Michael H. Tomasson

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Figure 4

ACA11 binds a noncanonical ribonucleoprotein complex consisting of a set of proteins implicated in RNA processing.

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ACA11 binds a noncanonical ribonucleoprotein complex consisting of a set...
(A) RNA EMSA confirming ACA11 binding to proteins from H929 cell nuclear extracts. Competitor, unlabeled ACA11 RNA. (B) Coomassie-stained SDS-PAGE gel of ACA11 pull-downs used for identification of proteins binding to ACA11 by MS. Representative proteins with the most abundant, unique peptides in each indicated band are marked with numbers that correspond to those in Table 2. M, protein marker. (C) Confirmation of ACA11-binding proteins by Western blot. The ACA11-protein complex was purified as in B and subjected to Western blot with antibodies to proteins identified by MS. The asterisk indicates nonspecific binding. Hsp90 was used as a negative control. (D) Confirmation of ACA11 presence in a DHX9/ILF3 ribonucleoprotein complex by CLIP followed by RT-PCR using H929 cells. H2O was used as a water template for RT-PCR. GAPDH was used as an internal control. M, DNA marker. (E) Physical interaction of ACA11 ribonucleoprotein complex proteins NCL, ILF3, ADAR, and HNRNPU with DHX9 in H929 cells was confirmed by immunoprecipitation.