The nucleotide and amino acid coding sequence of a gene for H1 histone that interacts with euchromatin. The early embryonic H1 gene of the sea urchin Strongylocentrotus purpuratus.

S Levy,I Sures,L Kedes

doi:10.1016/s0021-9258(18)34089-4

Abstract

We have determined the nucleotide sequence of the gene that codes for an H1 histone associated with euchromatin in the sea urchin Strongylocentrotus purpuratus. The gene codes for a protein of 205 amino acids. The nucleotide sequence of this gene is homologous to the sequence of H1 mRNA that is expressed during early embryonic development. We have compared the nucleotide and protein coding sequences of this H1 gene to those of the early H1 histone gene of the sea urchin Psammechinus miliaris. There is considerable drift by nucleotide substitution between the two genes randomly distributed across the mRNA coding region. Despite this divergence of nucleotide sequence, there are local constraints on amino acid substitutions throughout the molecule and especially in its central region. We have also compared the amino acid sequence in this central hydrophobic region of the euchromatic S. purpuratus H1 histone to the same region in H1 and H5 histones associated with heterochromatin. We show that certain amino acids are conserved and aligned in frameworks in all the sequenced H1 proteins.

Highlights

We have determined the nucleotide sequence of the Macleod et al (1977) noted thatthe central hydrophobic gene that codes for an HI histone associated with eu- region is the most conserved
The nucleotide sequence of this gene is homologous to acid sequence derived from the incomplete nucleotide sethe sequence of H1 mRNA that is expressed during quence of a Psammechinus miliaris Hg1ene
We show We report here thefmst complete nucleotide sequence of an that certain amino acids are conserved and aligned in H1 protein that interacts with euchromatin

Summary

RESULTS AND DISCUSSION

The nucleotidesequence of H1 from S. purpuratus was compared to the partial H1 gene sequence derived from P. One of the baseslong (Fig. 3).Bothsequencescontainthehallmark features of this protein is thaitt contains a number of repeti- heptanucleotide sequencemarking the 5’ end of the sea urchin tious oligopeptides at the COOH-terminalregion of the mol- histone mRNAs Nucleotide small DNA fragment (such as th2e0-base pair Pst I segment sequences downstream from thceoding region contain, in both in the middle of the H1 gene) We have overcome this poten- genes, a 26 base pairhomology that containsa s m d inverted tial problembysequencing theDNA usingtwodifferent repeat region (marked by arrows in Fig. 3) that may be a techniques: chemical degradation (Maxam and Gilbert,1977) transcription termination signal (Busslinger et al, 1979).The and primer extension with dideoxynucleotides (Sanger etal., 3’ untranslated trailer region of the mRNA is about 30-40 1977).In addition partsof the sequencewere confirmed by a bases long. A A GA A GG T GA C TA C TA A GA A GC C GG C CG C CC A CC C AC C GG C TG C CG A GA T GG T T

C A AG C AA T A

A A A GAGAAG AAG AAG A C TC C AA A G

A T CA A GA A G

K I K LV G L QTKG GASGSFKL