Histone H4 Acetylation of Euchromatin and Heterochromatin Is Cell Cycle Dependent and Correlated with Replication Rather Than with Transcription

Abstract

Reversible acetylation of nucleosomal histones H3 and H4 generally is believed to be correlated with potential transcriptional activity of eukaryotic chromatin domains. Here, we report that the extent of H4 acetylation within euchromatin and heterochromatic domains is linked with DNA replication rather than with transcriptional activity, whereas H3 acetylation remains fairly constant throughout the cell cycle. Compared with euchromatin, plant nucleolus organizers were more strongly acetylated at H4 during mitosis but less acetylated during S phase, when the nucleolus appeared to be (at least transiently) devoid of nucleosomes. Deposition-related acetylation of lysines 5 and 12 of H4 seems to be conserved in animals and plants and extended to K16 in plants. A possibly species-specific above-average acetylation at lysines 9/18 and 14 of H3 appeared in 4 ,6-diamidino-2-phenylindole (DAPI)-stained heterochromatin fractions. These results were obtained by combining immunodetection of all acetylatable isoforms of H3 and H4 on mitotic chromosomes and nuclei in G1, early S, mid-S, late S, and G2 phases of the field bean with identification of specific chromatin domains by fluorescence in situ hybridization or DAPI staining. In addition, the histone acetylation patterns of distinct domains were compared with their replication and transcription patterns. INTRODUCTIONThe histone proteins H2A, H2B, H3, and H4 form octamers that constitute the nucleosome core particles in all eukaryotes. Their N-terminal tails are subject to post-translational modifications such as acetylation, phosphorylation, methylation, ubiquitination, glycosylation, and ADP ribosylation (reviewed in Smith et al., 1995;Spencer and Davie, 1999).The reversible acetylation of N-terminal lysine residues at positions 5, 8, 12, and 16 of H4 and 9, 14, 18, and 23 of H3 mediates decondensation of the nucleosome structure (Loidl, 1988(Loidl, , 1994Garcia-Ramirez et al., 1995), alters histone-DNA interactions (Hong et al., 1993), and facilitates access and binding of transcription factors to genes transcribed by RNA polymerases II or III (Lee et al., 1993;Vettese-Dadey et al., 1996).A correlation between histone acetylation and potential transcriptional activity, initially proposed by Allfrey et al. (1964), has been proved in several cases (reviewed in Csordas, 1990;Turner, 1991Turner, , 1993Loidl, 1994;Grunstein, 1997;Struhl, 1998). According to one attractive recent hypothesis, histone modifications may constitute a concerted code to "specify unique downstream functions" (Strahl and Allis, 2000;Turner, 2000).After indirect immunolabeling with antibodies raised against acetylated isoforms of histone H4 (Turner and Fellows, 1989;, mammalian metaphase chromosomes show intense acetylation of euchromatic R-bands and less intense acetylation of constitutive and facultative heterochromatin (Jeppesen and Turner, 1993). The patterns of histone H4 acetylation described for plant chromosomes (Houben et al., 1996Belyaev et al., 1997;Vyskot et al., 1999) also reveal a below...

Comprehensive analysis of dynamics of histone H4 acetylation in mitotic barley cells

“…Consistent with this, transcription of rRNAs has been reported even at telophase (Roussel et al, 1996). In fact, strong acetylation in the NORs at metaphase has been reported in marsupials (Wakefield et al, 1997, Keohane et al, 1998 and Vicia faba (Houben et al, 1996, Belyaev et al, 1997, Jasencakova et al, 2000. In barley metaphase chromosomes, the NORs are strongly acetylated on histone H4 at K5 and K12 (Jasencakova et al, 2001).…”

“…Specific acetylation occurs on the newly synthesized histones in the cytoplasm (Sobel et al, 1995) and is required for DNA double-strand break repair (Bird et al, 2002). Replication-related histone acetylation is also reported in flow-sorted nuclei from field bean, barley, and Arabidopsis (Jasencakova et al, 2000(Jasencakova et al, , 2001(Jasencakova et al, , 2003.…”

New method to detect histone acetylation levels by flow cytometry

“…At the end of S phase, an increased HDAC activity was instead observed in concomitance of recruitment of HDAC2 on newly synthesized DNA (22). A precise timing in the synthesis of expressed and silenced genes has been consequently demonstrated, with the first and middle S phases devoted to replication of actively transcribed, hyper-acetylated chromatin (euchromatin), whereas DNA synthesis ends with silenced and hypo-acetylated chromatin (heterochromatin) reconstitution (23). Our flow cytometric data well fit into this scheme, as demonstrated by a first increase in histone acetylation signal detected in the G1 to S phase transition and by the appearance of a subpopulation characterized by lower acetylation signal close to the tetraploid DNA content (late S to G2M cell cycle phase) which can not simply related to the variation of the total amount of histone present in the cells.…”

NAD+-dependent deacetylation of H4 lysine 16 by class III HDACs

“…Acetylation of histone H3 and H4 have distinct functional and temporal patterns. Most histone H4 acetylation is cell-cycle dependent and peaks at the replicative S phase, whereas global H3 acetylation levels do not seem to vary (Jasencakova et al, 2000). During chromatin assembly in S phase, the newly synthesized H4 molecules are acetylated at lysines 5 and 12 and, after H3/H4 deposition during DNA replication the H4 molecules are rapidly deacetylated (Sobel et al, 1995;Polo and Almouzni, 2006).…”