Deletion of the unique gene encoding a typical histone H1 has no apparent phenotype in Aspergillus nidulans

We have cloned the H1 histone gene (hhoA) of Aspergillus nidulans. This sin gle-copy gene codes for a typical linker histone with one central globular domain. The open reading frame is interrupted by six introns. The position of the first intron is identical to that of introns found in some plant his tones. An H1-GFP fusion shows exclusive nuclear localization, whereas chrom osomal localization can be observed during condensation at mitosis. Surpris ingly, the deletion of hhoA results in no obvious phenotype. The nucleosoma l repeat length and susceptibility to micrococcal nuclease digestion of A. nidulans chromatin are unchanged in the deleted strain. The nucleosomal org anization of a number of promoters, including in particular the strictly re gulated niiA-niaD bidirectional promoter is not affected.