A novel protein with a RING finger motif near the amino terminus. Negative regulator of cold responses. Functions as an E3 ligase required for the ubiquitination of ICE1. HOS1 physically interacts with ICE1 and mediates the ubiquitination of ICE1 both in vitro and in vivo. Overexpression represses the expression of CBFs and their downstream genes and confers increased sensitivity to freezing stress. The mRNA is cell-to-cell mobile.
E3 ubiquitin-protein ligase that mediates ubiquitination and subsequent proteasomal degradation of the transcription factor ICE1. Acts as a negative regulator of cold signaling pathways (PubMed:16702557). Probably involved in recruiting the NUP107-160 subcomplex of the nuclear pore complex to chromatin (Probable). Controls flowering time in response to ambient temperatures (16 and 23 degrees Celsius) and intermittent cold, probably via the regulation of FT and TSF levels (PubMed:22960247).