title: Critical role of the ubiquitin ligase activity of UHRF1, a nuclear RING finger protein, in tumor cell growth.
abstract: Early cellular events associated with tumorigenesis often include loss of cell cycle checkpoints or alteration in growth signaling pathways. Identification of novel genes involved in cellular proliferation may lead to new classes of cancer therapeutics. By screening a tetracycline-inducible cDNA library in A549 cells for genes that interfere with proliferation, we have identified a fragment of UHRF1 (ubiquitin-like protein containing PHD and RING domains 1), a nuclear RING finger protein, that acts as a dominant negative effector of cell growth. Reduction of UHRF1 levels using an UHRF1-specific shRNA decreased growth rates in several tumor cell lines. In addition, treatment of A549 cells with agents that activated different cell cycle checkpoints resulted in down-regulation of UHRF1. The primary sequence of UHRF1 contains a PHD and a RING motif, both of which are structural hallmarks of ubiquitin E3 ligases. We have confirmed using an in vitro autoubiquitination assay that UHRF1 displays RING-dependent E3 ligase activity. Overexpression of a GFP-fused UHRF1 RING mutant that lacks ligase activity sensitizes cells to treatment with various chemotherapeutics. Taken together, our results suggest a general requirement for UHRF1 in tumor cell proliferation and implicate the RING domain of UHRF1 as a functional determinant of growth regulation.
authors.affiliation: Rigel Pharmaceuticals, South San Francisco, CA 94080, USA. yjenkins@rigel.com
authors.forename: Yonchu
authors.initials: Y
authors.lastname: Jenkins
authors.forename: Vadim
authors.initials: V
authors.lastname: Markovtsov
authors.forename: Wayne
authors.initials: W
authors.lastname: Lang
authors.forename: Poonam
authors.initials: P
authors.lastname: Sharma
authors.forename: Denise
authors.initials: D
authors.lastname: Pearsall
authors.forename: Justin
authors.initials: J
authors.lastname: Warner
authors.forename: Christian
authors.initials: C
authors.lastname: Franci
authors.forename: Betty
authors.initials: B
authors.lastname: Huang
authors.forename: Jianing
authors.initials: J
authors.lastname: Huang
authors.forename: George C
authors.initials: GC
authors.lastname: Yam
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Vistan
authors.forename: Erlina
authors.initials: E
authors.lastname: Pali
authors.forename: Jorge
authors.initials: J
authors.lastname: Vialard
authors.forename: Michel
authors.initials: M
authors.lastname: Janicot
authors.forename: James B
authors.initials: JB
authors.lastname: Lorens
authors.forename: Donald G
authors.initials: DG
authors.lastname: Payan
authors.forename: Yasumichi
authors.initials: Y
authors.lastname: Hitoshi
mesh_terms: D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology*; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D009369:Neoplasms / Q000201:enzymology*; D016376:Oligonucleotides, Antisense; D011994:Recombinant Proteins / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D014158:Transcription, Genetic; D044767:Ubiquitin-Protein Ligases
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D016376:Oligonucleotides, Antisense; D011994:Recombinant Proteins; C406364:UHRF1 protein, human; D044767:Ubiquitin-Protein Ligases