Carl D. Novina
MicroRNAs are non-coding, endogenous, ~21-nucleotide-long RNAs that play key roles in numerous cellular processes such as maintenance of embryonic and somatic stem cells; differentiation and development of cells, tissues, organs, and organ systems; and a wide spectrum of cell-specific functions. It is not surprising, therefore, that microRNA dysregulation is associated with numerous diseases, especially cancers. Research in the Novina laboratory focuses on (1) the fundamental biology of microRNAs and (2) their altered function in cancers. Our work combines hypothesis-driven, discovery-driven, and computation-driven approaches to identify microRNAs, their target mRNAs, and the effectors and regulators of microRNA activities.
To understand the molecular details of miRNAs function, we developed the first cell-free, miRNA-directed translational repression reactions (Mol. Cell 2006, PNAS 2008). Using this cell-free system, we can selectively add or remove microRNAs, mRNAs, or proteins from the repression reactions to define the roles for each constituent in microRNA function. Additionally, the effects of particular modifications to microRNAs, mRNAs, or proteins can be studied in a controlled setting. To complement in vitro approaches to microRNA function, we engineered cells in which a robustly-expressed, endogenous microRNA (miR-21) inhibits translation of a reporter mRNA. We have used genetic screening approaches to identify factors that mediate or regulate microRNA function. We also use confocal microscopy and FRET-based approaches to visualize microRNA-containing repressive complexes in the cells.
MicroRNA expression is frequently altered during cancer initiation and progression. Detecting which microRNAs are altered can help identify not only the presence of cancer and the type of cancer but also can help determine the prognosis and likelihood of responding to particular therapies. Determining the basis of altered microRNA expression and function can also provide fundamental insights into the mechanisms of oncogenesis. We recently used microRNA expression profiling of human chronic lymphocytic leukemia (CLL) patient samples to discern an activated B cell-like phenotype in CLL cells (PLoSONE, 2011). Generally, CLL cells are not thought to represent activated B cells. However, microRNA expression profiling identified certain microRNA changes in CLL cells characteristic of B cells stimulated by B cell activators. For example, our data indicate up-regulation of miR-29c and down-regulation of miR-233 in activated donor B cells and in CLL patient cells. Importantly, up-regulation of miR-29c and down-regulation of miR-223 are associated with increased time to first treatment, a poor prognostic indicator for CLL. These data imply that miR-29c and miR-223 might be targets for therapeutic inhibition and reconstitution, respectively.
In another project, we identified microRNA changes that are essential for initiation and maintenance of T cell acute lymphoblastic leukemia (T-ALL; JEM 2011). A driver oncogene for T-ALL is NOTCH1 which has been shown to transcriptionally activate MYC, another critical T-ALL oncogene. Collaborating with the von Boehmer and Look laboratories, we found that induction of NOTCH1 led to the reduction of miR-451 and miR-709 and that both microRNAs directly target MYC for repression. By reconstituting these microRNAs in mouse models of T-ALL, we demonstrated for the first time that reduced expression of any microRNAs was required for tumor initiation. Moreover, gamma secretase inhibitors (which prevents cleavage and activation of NOTCH1) are currently in clinical trials for treatment of human T-ALL. Our studies also found that reduced expression of miR-451 was important for human T-ALL sensitivity to gamma secretase inhibitors.
For a more complete description of research in the Novina laboratory, please visit http://research.dfci.harvard.edu/rnai
microRNA expression profiling identifies activated B cell status in chronic lymphocytic leukemia cells. Li S, Moffett HF, Lu J, Werner L, Zhang H, Ritz J, Neuberg D, Wucherpfennig KW, Brown JR, Novina CD. PLoS ONE. 2011. 2011; Mar 8;6(3):e16956. PMID: 21408091
Repression of tumor suppressor miR-451 is essential for NOTCH1-induced oncogenesis in T-ALL. Li X, Sanda T, Look AT, Novina CD, von Boehmer H. J. Exp. Med. 2011. Apr 11;208(4):663-75. Epub 2011 Apr 4. PMID: 21464222
Intronic miR-211 assumes the tumor suppressive function of its host gene in melanoma. Levy C, Khaled M, Iliopoulos D, Janas M, Schubert S, Pinner S, Chen P-H, Li S, Fletcher A, Yokoyama S, Scott KL, Garraway LA, Song JS, Granter SR, Turley SJ, Fisher DE, and Novina CD. Mol. Cell. 2010 Dec 10;40(5):841-9. Epub 2010 Nov 25. PMID: 21109473
Distinct passenger strand and mRNA cleavage activities of human Argonaute proteins. Wang B, Li S, Qi HH, Chowdhury D, Shi Y, and Novina CD. Nat. Struct. Mol. Biol. 2009; 16(12):1259-1266. PMID: 19946268
MicroRNA-repressed mRNAs contain 40S but not 60S components. Wang B, Yanez A, Novina CD. Proc. Natl. Acad. Sci. U S A 2008 Apr 8;105(14):5343-8. PMID: 18390669
Last Update: 1/6/2014