In contrast, mechanisms whereby abiotic stress regulated genes are kept silent in the absence of stress has not been well investigated. kinase assay To silence gene ex pression, eukaryotes employ transcriptional repression as a key regulatory mechanism. Transcriptional repres sion plays a critical role in cell fate specification and body patterning in both animals Inhibitors,Modulators,Libraries and plants. Tran scriptional activation and repression occur within the context of chromatin organization in eukaryotes. Inhibitors,Modulators,Libraries Chro matin structure is a governed process often associated with epigenetic regulation, namely, histone post translational modifications, histone variants and DNA methylation that alter chromatin compaction resulting in altered accessibility of genes to transcriptional regula tion.
Transcriptional repression is mediated by an import ant and extensively studied class of co repressors, those belonging to the Gro/Tup1 family, including Tup1 in yeast, Groucho in Dros ophila, and Transducin like enhancer of split in mammals. These co repressor proteins, collectively called the Gro/Tup1 family, do not possess direct DNA binding capability. They repress Inhibitors,Modulators,Libraries a diverse number of target genes through targeted recruitment to the DNA template via protein protein interactions with a variety of DNA bound transcription factors to mediate repression. The Gro/Tup1 family consists of 13 members in Ara bidopsis, and the functions of only a few have been stud ied. LEUNIG was the first Gro/Tup1 family member to be characterized in Arabidopsis. The LUG protein has LisH and LUFS domains at the N terminus, and resembles Gro/Tup1 in having a Q rich and seven WD domains.
The LisH domain is a dimerization motif that is present in all plant Gro/Tup1 proteins. The LUFS domain is present only in LUG and LUH among the Gro/Tup1 family members present in Arabidopsis. Inhibitors,Modulators,Libraries LUFS domain is involved in protein protein interactions. The LUFS domain in LUG interacts physically Inhibitors,Modulators,Libraries with SEUSS, a Q rich protein with a conserved domain that is similar to the dimerization domain of the LIM domain binding family of transcriptional co regulators in mouse and Drosophila. SEU forms a co repressor complex with LUG and acts as an adapter between LUG and a variety of transcription factors to mediate repres sion of diverse target genes during floral organ identity, floral patterning and abaxial organ identity in leaves. LUH is another member of the Gro/Tup1 family and highly similar to LUG with 44% identity in Arabidopsis. Thus, not surprisingly LUH functions redun dantly to some extent with LUG in abaxial organ iden tity in leaves and identity make it clear of floral organs.