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Ahyar Ahmad
Biochemistry and Biotechnology Lab., Department of Chemistry, Faculty of Natural Sciences, Hasanuddin University, Makassar 90245
Chemical Engineering, Chemistry & Bioengineering Chemistry

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MUTATION ON WD DIPEPTIDE MOTIFS OF THE p48 SUBUNIT OF CHROMATIN ASSEMBLY FACTOR-1 CAUSING VIABILITY AND GROWTH OF DT40 CHICKEN B CELL LINE Ahyar Ahmad; Harningsih Karim
Indonesian Journal of Chemistry Vol 10, No 2 (2010)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (795.816 KB) | DOI: 10.22146/ijc.21468

Abstract

Chromatin assembly factor-1 (CAF-1), a protein complex consisting of three subunits, p150, p60, and p48, is highly conserved from yeast to humans and facilitated nucleosome assembly of newly replicated DNA. The p48 subunit, CAF-1p48 (p48), with seven WD (Trp-Asp) repeat motifs, is a member of the WD protein family. The immunoprecipitation experiment revealed that ß-propeller structure of p48 was less stringent for it's binding to HDAC-1, but more stringent for its binding to both histones H4 and CAF-1p60 but not to ASF-1, indicating that the proper ß-propeller structure of p48 is essential for the binding to these two proteins histone H4 and CAF-1p60. Complementation experiments, involving missense and truncated mutants of FLAG-tagged p48, revealed that mutations of every of seven WD dipeptide motifs, like both the N-terminal and C-terminal truncated mutations, could not rescue for the tet-induced lethality. These results indicate not only that p48 is essential for the viability of vertebrate cells, although the yeast p48 homolog is nonessential, but also that all the seven WD dipeptide motifs are necessary for the maintenance of the proper structure of p48 that is fundamentally important for cell viability.
EFFECT OF HIRA PROTEIN ON TRANSCRIPTIONAL REGULATIONS OF GENES IN VERTEBRATE CELLS Ahyar Ahmad
Indonesian Journal of Chemistry Vol 8, No 3 (2008)
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1530.786 KB) | DOI: 10.22146/ijc.21605

Abstract

For better understanding of DNA replicating-coupled chromatin assembly and transcription regulation in eukaryotes, we studied biochemical and genetic analysis of nuclear-related proteins from chicken DT40 cell lines. The genetic analysis of some nuclear proteins, such as HIRA and CAF-1, indicated that these proteins could play overlapping roles in chromatin dynamics and is consistent with the finding that HIRA protein exhibited binding ability to histones and ASF-1, as also ASF-1 bound directly with CAF-1p60. In this study, revealed not only that the N-terminal and C-terminal halves of HIRA mediate individually transcription repressions but also that even one of the seven WD dipeptide motifs and the LXXLL motif of HIRA are required for these mediations in vivo. Finally, we found that HIRA-mediated repression is sensitive to tricostatin TSA and it co-represses transcription together with HDAC-2. We believe our findings will contribute to a major break-through in future studies on the specific, individual roles of HIRA involved in numerous DNA-utilizing processes, through the formation and/or maintenance of the chromatin structure in vertebrate cells.
Co-Authors Harningsih Karim