The Histone H1 Genes of the Dipteran Insect, Chironomus thummi, Fall under Two Divergent Classes and Encode Proteins with Distinct Intranuclear Distribution and Potentially Different Functions

Abstract

Four histone H1 genes of the midge, Chironomus rhummi piger, and three H1 genes of the subspecies C. thummi thummi have been cloned and assigned to the four different HI proteins from C. thummi larvae. Together with an earlier cloned HI gene from C. thummi thummi [Hankeln, T. & Schmidt, E. R. (1991) Chromosoma 101, 25-31], these genes probably constitute the complete complement of H1 genes in both subspecies. They were found to fall under two classes that differ remarkably in their gene copy numbers, genomic organization, structure of flanking sequences, codon usage, and expression during embryonic development, and that encode HI proteins of divergent structure. Histone HI 1-1 contains an inserted sequence, KAPKAPKAPKSPKAE in C. thummi piger, and KAPKAPKSPKAE in C. thummi thummi, that is lacking in the other H I variants, H1 11-1, H1 11-2, and H I 111-1. In the immediate neighbourhood to the inserted sequence, a substitution in the HI 1-1 protein sequence dramatically enhances the potential to form a reversed turn. In early development, HI 1-1 is expressed at a higher rate than the other HI genes. The transcripts have a size of about 1 kb; in addition, the HI I-1 gene exhibited two minor transcripts of about 2.5 and > 3 kb size in middle blastoderm that are possibly polyadenylated. Together with our earlier finding that histone HI 1-1 is found in a limited number of polytene chromosome bands whereas the other H1 histones are uniformly distributed in chromatin, these results intimate functional differences between the two classes of HI genes and their products.

PCR cloning of a histone H1 gene from Anopheles stephensi mosquito cells: comparison of the protein sequence with histone H1-like, C-terminal extensions on mosquito ribosomal protein S6

“…There is a single recorded His1 allele in Drosophila [8], while multiple histone H1 variants have been described in Chironomid flies [9-11]. When the deduced sequence of the Drosophila histone H1 protein (Accession NM_058232) was compared to the Anopheles gambiae genome using the program BLAST [12] on the NCBI website (National Center for Biotechnology Information; ), we obtained 5 accessions with E values ranging from 3e-35 to 8e-43, distributed on mosquito chromosomes 2 and 3.…”

Phenotypic effect of substitution of allelic variants for a histone H1 subtype specific for growing tissues in the garden pea (Pisum sativum L.)

“…However, in mammals, it was shown that total amount of H1 is critical and cannot be reduced under a certain level . H1 is often represented by a number of subtypes which may have different chromosomal location (Trieschmann et al 1997;Tanaka et al 1999;Th'ng et al 2005). However, histone H1 binding to DNA is unstable and reversible, so chromosomal location of its subtypes results from a turnover and is a highly dynamic equilibrium (Bustin et al 2005).…”

Dynamic alterations of linker histone variants during development

“…Ironically, the first description of an oocyte-specific linker histone actually predated the original discovery of a testis-specific H1 subtype, when a «cleavage stage» histone was characterized in sea urchin (Ruderman and Gross, 1974). This was soon followed by descriptions of histone subtype switches during embryo development in such diverse organisms as the mud snail, Ilyanassa obsoleta; two frogs, Xenopus laevis and Bufo japonicus; the midge, Chironomus thummi; mouse; the zebrafish, Danio rerio; and, finally, in humans as well (Flenniken & Newrock, 1987;Smith et al, 1988;Ohsumi and Katagiri, 1991;Trieschmann et al, 1997;Tanaka et al, 2001;Wibrand and Olsen, 2002;Muller et al, 2002; , Fig. 4).…”