Chromatin modulating proteins are thought to be involved in multimeric protein-protein interactions and contain characteristic amino-acid motifs like the SET domain. The SET domain proteins are believed to regulate gene expression and chromatin structure via lysine histone methyltransferase (HMT) activity. SET domain proteins can generally be divided into activators (H3K4 methyltransferases) and repressors (H3K9 methyltransferases).These proteins often reside and function in protein complexes.
The Arabidopsis thaliana protein ATX4 belongs to the trithorax subgroup of SET-domain proteins. ATX4 shows sequence similarity with other H3K4 methyltransferases and is probably a positive regulator of homeotic genes during plant development.
This thesis comprises expressional and functional analysis of the actively transcribed SET-domain encoding gene ATX4.
Expression pattern was analysed by promoter::GUS fusion constructs and bioinformatics. Promoter::GUS analysis indicates expression in vascular tissue, pollen and the papilla of the stigma of Arabidopsis thaliana.
Yeast two-hybrid screens provided new putative interacting partners for ATX4. In addition deletion mapping shows that the interacting partners bind specific parts of the ATX4 protein. GST pull-down has been performed to confirm one of these reactions.
T-DNA insertion lines for ATX4 show an early flowering phenotype. ATX4 mutant plants shoots earlier and grow faster than wild type plants. This may indicate a regulatory role for ATX4 on flowering time as a putative activator of Flowering Locus C (FLC).