title: Transcriptional coactivator PC4, a chromatin-associated protein, induces chromatin condensation.
abstract: Human transcriptional coactivator PC4 is a highly abundant multifunctional protein which plays diverse important roles in cellular processes, including transcription, replication, and repair. It is also a unique activator of p53 function. Here we report that PC4 is a bona fide component of chromatin with distinct chromatin organization ability. PC4 is predominantly associated with the chromatin throughout the stages of cell cycle and is broadly distributed on the mitotic chromosome arms in a punctate manner except for the centromere. It selectively interacts with core histones H3 and H2B; this interaction is essential for PC4-mediated chromatin condensation, as demonstrated by micrococcal nuclease (MNase) accessibility assays, circular dichroism spectroscopy, and atomic force microscopy (AFM). The AFM images show that PC4 compacts the 100-kb reconstituted chromatin distinctly compared to the results seen with the linker histone H1. Silencing of PC4 expression in HeLa cells results in chromatin decompaction, as evidenced by the increase in MNase accessibility. Knocking down of PC4 up-regulates several genes, leading to the G2/M checkpoint arrest of cell cycle, which suggests its physiological role as a chromatin-compacting protein. These results establish PC4 as a new member of chromatin-associated protein family, which plays an important role in chromatin organization.
authors.affiliation: Transcription and Disease Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India.
authors.forename: Chandrima
authors.initials: C
authors.lastname: Das
authors.forename: Kohji
authors.initials: K
authors.lastname: Hizume
authors.forename: Kiran
authors.initials: K
authors.lastname: Batta
authors.forename: B R Prashanth
authors.initials: BR
authors.lastname: Kumar
authors.forename: Shrikanth S
authors.initials: SS
authors.lastname: Gadad
authors.forename: Semanti
authors.initials: S
authors.lastname: Ganguly
authors.forename: Stephanie
authors.initials: S
authors.lastname: Lorain
authors.forename: Alain
authors.initials: A
authors.lastname: Verreault
authors.forename: Parag P
authors.initials: PP
authors.lastname: Sadhale
authors.forename: Kunio
authors.initials: K
authors.lastname: Takeyasu
authors.forename: Tapas K
authors.initials: TK
authors.lastname: Kundu
mesh_terms: D002453:Cell Cycle; D002843:Chromatin / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D002875:Chromosomes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D008677:Metaphase; D018625:Microscopy, Atomic Force; D020411:Oligonucleotide Array Sequence Analysis; D034741:RNA, Small Interfering; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D006657:Histones; D034741:RNA, Small Interfering; C509201:SUB1 protein, human; D014157:Transcription Factors