Identification and Characterization of the Genes Encoding the Core Histones and Histone Variants of Neurospora crassa

Corresponding author: Eric U. Selker, University of Oregon, Eugene, OR 97403-1229., selker{at}molbio.uoregon.edu (E-mail)

Communicating editor: R. H. DAVIS

We have identified and characterized the complete complement of genes encoding the core histones of Neurospora crassa. In addition to the previously identified pair of genes that encode histones H3 and H4 (hH3 and hH4-1), we identified a second histone H4 gene (hH4-2), a divergently transcribed pair of genes that encode H2A and H2B (hH2A and hH2B), a homolog of the F/Z family of H2A variants (hH2Az), a homolog of the H3 variant CSE4 from Saccharomyces cerevisiae (hH3v), and a highly diverged H4 variant (hH4v) not described in other species. The hH4-1 and hH4-2 genes, which are 96% identical in their coding regions and encode identical proteins, were inactivated independently. Strains with inactivating mutations in either gene were phenotypically wild type, in terms of growth rates and fertility, but the double mutants were inviable. As expected, we were unable to isolate null alleles of hH2A, hH2B, or hH3. The genomic arrangement of the histone and histone variant genes was determined. hH2Az and the hH3-hH4-1 gene pair are on LG IIR, with hH2Az centromere-proximal to hH3-hH4-1 and hH3 centromere-proximal to hH4-1. hH3v and hH4-2 are on LG IIIR with hH3v centromere-proximal to hH4-2. hH4v is on LG IVR and the hH2A-hH2B pair is located immediately right of the LG VII centromere, with hH2A centromere-proximal to hH2B. Except for the centromere-distal gene in the pairs, all of the histone genes are transcribed toward the centromere. Phylogenetic analysis of the N. crassa histone genes places them in the Euascomycota lineage. In contrast to the general case in eukaryotes, histone genes in euascomycetes are few in number and contain introns. This may be a reflection of the evolution of the RIP (repeat-induced point mutation) and MIP (methylation induced premeiotically) processes that detect sizable duplications and silence associated genes.

This article has been cited by other articles:

				K. K. Adhvaryu and E. U. Selker Protein phosphatase PP1 is required for normal DNA methylation in Neurospora Genes & Dev., December 15, 2008; 22(24): 3391 - 3396. [Abstract] [Full Text] [PDF]

				J. Linger and J. K. Tyler Global Replication-Independent Histone H4 Exchange in Budding Yeast Eukaryot. Cell, October 1, 2006; 5(10): 1780 - 1787. [Abstract] [Full Text] [PDF]

				K. K. Adhvaryu, S. A. Morris, B. D. Strahl, and E. U. Selker Methylation of Histone H3 Lysine 36 Is Required for Normal Development in Neurospora crassa Eukaryot. Cell, August 1, 2005; 4(8): 1455 - 1464. [Abstract] [Full Text] [PDF]

				K. A. Borkovich, L. A. Alex, O. Yarden, M. Freitag, G. E. Turner, N. D. Read, S. Seiler, D. Bell-Pedersen, J. Paietta, N. Plesofsky, et al. Lessons from the Genome Sequence of Neurospora crassa: Tracing the Path from Genomic Blueprint to Multicellular Organism Microbiol. Mol. Biol. Rev., March 1, 2004; 68(1): 1 - 108. [Abstract] [Full Text] [PDF]

				H. D. Folco, M. Freitag, A. Ramon, E. D. Temporini, M. E. Alvarez, I. Garcia, C. Scazzocchio, E. U. Selker, and A. L. Rosa Histone H1 Is Required for Proper Regulation of Pyruvate Decarboxylase Gene Expression in Neurosporacrassa Eukaryot. Cell, April 1, 2003; 2(2): 341 - 350. [Abstract] [Full Text] [PDF]