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Crystal Structure of RBBP4-peptide complex
Structural highlights
FunctionRBBP4_HUMAN Core histone-binding subunit that may target chromatin assembly factors, chromatin remodeling factors and histone deacetylases to their histone substrates in a manner that is regulated by nucleosomal DNA. Component of several complexes which regulate chromatin metabolism. These include the chromatin assembly factor 1 (CAF-1) complex, which is required for chromatin assembly following DNA replication and DNA repair; the core histone deacetylase (HDAC) complex, which promotes histone deacetylation and consequent transcriptional repression; the nucleosome remodeling and histone deacetylase complex (the NuRD complex), which promotes transcriptional repression by histone deacetylation and nucleosome remodeling; the PRC2/EED-EZH2 complex, which promotes repression of homeotic genes during development; and the NURF (nucleosome remodeling factor) complex.[1] Publication Abstract from PubMedSal-like 4 (SALL4) is a nuclear factor central to the maintenance of stem cell pluripotency and is a key component in hepatocellular carcinoma, a malignancy with no effective treatment. In cancer cells, SALL4 associates with nucleosome remodeling deacetylase (NuRD) to silence tumor-suppressor genes, such as PTEN. Here, we determined the crystal structure of an amino-terminal peptide of SALL4(1-12) complexed to RBBp4, the chaperone subunit of NuRD, at 2.7 A, and subsequent design of a potent therapeutic SALL4 peptide (FFW) capable of antagonizing the SALL4-NURD interaction using systematic truncation and amino acid substitution studies. FFW peptide disruption of the SALL4-NuRD complex resulted in unidirectional up-regulation of transcripts, turning SALL4 from a dual transcription repressor-activator mode to singular transcription activator mode. We demonstrate that FFW has a target affinity of 23 nM, and displays significant antitumor effects, inhibiting tumor growth by 85% in xenograft mouse models. Using transcriptome and survival analysis, we discovered that the peptide inhibits the transcription-repressor function of SALL4 and causes massive up-regulation of transcripts that are beneficial to patient survival. This study supports the SALL4-NuRD complex as a drug target and FFW as a viable drug candidate, showcasing an effective strategy to accurately target oncogenes previously considered undruggable. Targeting cancer addiction for SALL4 by shifting its transcriptome with a pharmacologic peptide.,Liu BH, Jobichen C, Chia CSB, Chan THM, Tang JP, Chung TXY, Li J, Poulsen A, Hung AW, Koh-Stenta X, Tan YS, Verma CS, Tan HK, Wu CS, Li F, Hill J, Joy J, Yang H, Chai L, Sivaraman J, Tenen DG Proc Natl Acad Sci U S A. 2018 Jul 5. pii: 1801253115. doi:, 10.1073/pnas.1801253115. PMID:29976840[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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