Multiple myeloma–associated chromosomal translocation activates orphan snoRNA ACA11 to suppress oxidative stress
Liang Chu, … , Ravi Vij, Michael H. Tomasson
Liang Chu, … , Ravi Vij, Michael H. Tomasson
Published July 2, 2012
Citation Information: J Clin Invest. 2012;122(8):2793-2806. https://doi.org/10.1172/JCI63051.
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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 7

ACA11 provides evidence for the t(4;14) gene signature in part — ACA11 is sufficient to downregulate RP genes.

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ACA11 provides evidence for the t(4;14) gene signature in part — ACA11 i...
(A) Overexpression of ACA11 confirmed by Northern blot analysis in Arf–/– MEFs stably transduced with ACA11 lentiviruses. β-Actin was used as loading control. (B) Overexpression of ACA11 in Arf–/– MEFs as measured by qRT-PCR. (C) RP mRNA expression in Arf–/– MEFs overexpressing ACA11 was analyzed by qRT-PCR. (D) Expression of RPs in Arf–/– MEFs overexpressing ACA11 demonstrated by Western blot. γ-Tubulin was used as loading control. (E) Overexpression of ACA11 confirmed by Northern blot analysis in MM.1S cells stably transduced with ACA11 lentiviruses. β-Actin was used as loading control. (F) qRT-PCR showing the expression of ACA11 in MM.1S cells in E. (G) RP mRNA expression in MM.1S cells overexpressing ACA11 was analyzed by qRT-PCR. (H) Downregulation of RPs in MM.1S cells overexpressing ACA11 demonstrated by Western blot. γ-Tubulin was used as loading control. (I) Small RNAs were isolated from MM.1S cells overexpressing ACA11. snoRNA expression was analyzed by qRT-PCR. U43, snoRNA located in RPL3; U64, snoRNA located in RPS2; U32A, U33, and U35A, snoRNAs located in RPL13A. qRT-PCR data were normalized to the average of 3 reference genes, (B, C, F, and G) GAPDH, UBC, and YWHAZ or (I) U6, U44, and U48, and are shown as fold change relative to that of mock-treated cells. Data represent mean ± SD (n = 3). *P < 0.05, **P < 0.01.