Nucleotide sequence and expression of a maize H1 histone cDNA

Area of Science:

• Molecular Biology
• Plant Genetics
• Biochemistry

Background:

• Histone H1 proteins are crucial for chromatin structure and gene regulation.
• The complete amino acid sequence of H1 histone from monocotyledonous plants was previously unknown.
• Understanding plant H1 histone diversity is essential for comprehending chromatin organization in plants.

Purpose of the Study:

• To determine the complete amino acid sequence of a H1 histone from a monocotyledonous plant (maize).
• To analyze the structural features and evolutionary conservation of the maize H1 histone.
• To investigate the gene family size and expression patterns of H1 histone genes in maize.

Main Methods:

• Isolation of cDNA from a maize library.
• Deduction of amino acid sequence from cDNA.
• Sequence homology analysis with other H1 proteins (dicots and animals).
• Southern-blot hybridization to analyze gene family size.
• Analysis of gene expression patterns.

Main Results:

• The first complete amino acid sequence of a monocot H1 histone (maize) was determined; it is 245 amino acids long and exhibits a tripartite structure.
• The central globular region shows 60% homology with dicot H1 proteins but only 20% with animal H1 proteins, though key nucleosome-binding residues are conserved.
• The C-terminal region contains a highly basic, repetitive element (KA/PKXA/PAKA/PK).
• Southern blots indicate H1 histone is encoded by a small multigene family, with homologous families found in other plant species.
• Gene expression patterns are similar to core histones during germination and in adult tissues.

Conclusions:

• The maize H1 histone shares conserved structural features with other H1 proteins, particularly in regions important for nucleosome interaction.
• Plant H1 histones, like the maize H1, possess unique features such as an N-terminal region with balanced acidic and basic residues.
• The H1 histone in maize is part of a multigene family with expression patterns comparable to core histones, suggesting conserved roles in chromatin organization.