Mouse anti-Human SAFB2 monoclonal antibody, clone 5I4

Many microRNAs (miRNAs) are generated from primary transcripts containing multiple clustered stem-loop structures that are thought to be recognized and cleaved by the Microprocessor complex as independent units. Here, we uncover an unexpected mode of processing of the bicistronic miR-15a-16-1 cluster. We find that the primary miR-15a stem-loop is not processed on its own but that the presence of the neighboring primary miR-16-1 stem-loop on the same transcript can compensate for this deficiency in cis. Using a CRISPR/Cas9 screen, we identify SAFB2 (scaffold attachment factor B2) as an essential co-factor in this miR-16-1-assisted pri-miR-15 cleavage and describe SAFB2 as an accessory protein of the Microprocessor. Notably, SAFB2-mediated cleavage expands to other clustered pri-miRNAs, indicating a generalmechanism. Together, our study reveals an unrecognized function of SAFB2 in miRNA processing and suggests a scenario in which SAFB2 enables the binding and processing of suboptimal Microprocessor substrates in clustered primary miRNA transcripts.

A significant amount of nuclear p53 is found associated with the nuclear matrix in cells that were exposed to genotoxic stress. In this study we identified Scaffold attachment factor B1 (SAFB1), a nuclear matrix-associated protein that binds the scaffold or matrix attachment regions (S/MARs) of genomic DNA, as a novel p53-interacting protein. SAFB1 was able to associate with p53 through its C-terminal domain, while significant co-localization of the two proteins was observed in cells treated with 5-fluorouracil or mithramycin. Binding of p53 to SAFB1 had a significant functional outcome, since SAFB1 was shown to suppress p53-mediated reporter gene expression. These data suggest that nuclear matrix-associated proteins may play a critical role in regulating p53 localization and activity. Structured summary: p53 physically interacts with SRPK1a:shown by two hybrid (view interaction) p53 physically interacts with SRPK1a:shown by pull down (view interaction) p53 physically interacts with SRPK1a:shown by anti bait coimmunoprecipitation (view interaction) p53 physically interacts with SRPK1a:shown by anti tag coimmunoprecipitation (view interaction) SAFB1 physically interacts with p53:shown by pull down (view interactions 1, 2) SAFB1 physically interacts with p53:shown by anti bait coimmunoprecipitation (view interactions 1, 2) SAFB1 and p53 colocalize:shown by fluorescence microscopy (view interaction) SAFB2 physically interacts with p53:shown by pull down (view interaction) (C) 2010 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.