title: PHF6 regulates cell cycle progression by suppressing ribosomal RNA synthesis.
abstract: Mutation of PHF6, which results in the X-linked mental retardation disorder Börjeson-Forssman-Lehmann syndrome, is also present in about 38% of adult T-cell acute lymphoblastic leukemias and 3% of adult acute myeloid leukemias. However, it remains to be determined exactly how PHF6 acts in vivo and what functions of PHF6 may be associated with its putative tumor suppressor function. Here, we demonstrate that PHF6 is a nucleolus, ribosomal RNA promoter-associated protein. PHF6 directly interacts with upstream binding factor (UBF) through its PHD1 domain and suppresses ribosomal RNA (rRNA) transcription by affecting the protein level of UBF. Knockdown of PHF6 impairs cell proliferation and arrests cells at G(2)/M phase, which is accompanied by an increased level of phosphorylated H2AX, indicating that PHF6 deficiency leads to the accumulation of DNA damage in the cell. We found that increased DNA damage occurs at the ribosomal DNA (rDNA) locus in PHF6-deficient cells. This effect could be reversed by knocking down UBF or overexpressing RNASE1, which removes RNA-DNA hybrids, suggesting that there is a functional link between rRNA synthesis and genomic stability at the rDNA locus. Together, these results reveal that the key function of PHF6 is involved in regulating rRNA synthesis, which may contribute to its roles in cell cycle control, genomic maintenance, and tumor suppression.
authors.affiliation: Department of Experimental Radiation Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Jiadong
authors.initials: J
authors.lastname: Wang
authors.forename: Justin Wai-chung
authors.initials: JW
authors.lastname: Leung
authors.forename: Zihua
authors.initials: Z
authors.lastname: Gong
authors.forename: Lin
authors.initials: L
authors.lastname: Feng
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Shi
authors.forename: Junjie
authors.initials: J
authors.lastname: Chen
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002453:Cell Cycle; D002466:Cell Nucleolus / Q000378:metabolism; D049109:Cell Proliferation; D004249:DNA Damage / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D059565:G2 Phase Cell Cycle Checkpoints; D055785:Gene Knockdown Techniques; D056426:Genetic Loci / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis; D009692:Nucleic Acid Heteroduplexes / Q000378:metabolism; D035463:Pol1 Transcription Initiation Complex Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D012097:Repressor Proteins
chemical_list: D002352:Carrier Proteins; D004275:DNA, Ribosomal; D009692:Nucleic Acid Heteroduplexes; C502542:PHF6 protein, human; D035463:Pol1 Transcription Initiation Complex Proteins; D012335:RNA, Ribosomal; D012097:Repressor Proteins; C063844:transcription factor UBF