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 8

ACA11 functions to modulate oxidative stress, cell proliferation, and resistance to chemotherapy.

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ACA11 functions to modulate oxidative stress, cell proliferation, and re...
(A and B) ROS levels, quantified by DCFH-DA (DCF) labeling, are suppressed by ACA11 expression in (A) Arf–/– MEFs or (B) MM.1S cells at baseline and upon challenge with hydrogen peroxide (H2O2). (C and D) ACA11 expression increased growth and proliferation of MM.1S cells as measured by (C) cell counting and (D) BrdU-ELISA relative to mock-treated cells. (E) ACA11 increased resistance of MM.1S cells to cytotoxic chemotherapy as measured by MTT viability assay. (F and G) Northern blot and qRT-PCR analyses of ACA11 knockdown in H929 cells 4 days after transfection with ASOs. β-Actin was used as loading control. U23, unrelated snoRNA. αA2 and αA3 are ASOs that target ACA11. (H–K) Knockdown of ACA11 in H929 cells (H) increased ROS levels, (I) decreased cell growth, (J) decreased cell proliferation, and (K) decreased resistance to cytotoxic chemotherapy. (L and N) Growth of (L) KMS-11 and (N) RPMI8226 cells in immunocompromised mice is reduced by ACA11 knockdown. (M and O) qRT-PCR showing the expression of ACA11 in (M) KMS-11 and (O) RPMI8226 xenograft tumors. Cells were nucleofected with 600 pmol ASOs per 106 cells and cultured for (I) 24 hours or (H, J–L, and N) 48 hours before further analysis. qRT-PCR data in G, M, and O were normalized to the average of 3 reference genes (GAPDH, UBC, YWHAZ) and are shown as fold change relative to that of mock-treated cells. All data shown represent mean ± SD (n = 3 [A–E and G–K], n = 5 [L–O]). *P < 0.05, **P < 0.01.