Lsh subfamily

The Lsh subfamily takes its name from the mouse Lsh (lymphoid specific helicase) protein 1, although it is widely expressed and no helicase activity has been detected. The official name for both the mouse and human proteins is HELLS (Helicase Lymphoid Specific), although the human protein is more often referred to as LSH, PASG or SMARCA6. Mutants lead to premature aging with cells exhibiting replicative senescence 2. Importantly, global loss of CpG methylation is observed in mammalian mutant cell lines and the Arabidopsis thaliana homologue, DDM1 3, 4. It has also been found that Lsh is localised to heterochromatic regions providing additional support for involvement in the molecular events related to DNA methylation 5. Interestingly, evidence has been presented that Arabidopsis DDM1 can slide nucleosomes in vitro 6.

Lsh members are found over a very broad range of eukaryotes including not only fungi, plants and animals but also protists such as plasmodia and kinetoplastids. In many of these organisms the function of Lsh must be independent of DNA methylation. The S cerevisiae member at locus YFR038W has no systematic name and deletion strains are viable. However, our genome scans also did not identify Lsh subfamily proteins in a number of lower animals, or in S pombe. This may represent functional redundancy or difficulties in distinguishing very distant homologues relative to related subfamilies.

names associated with subfamily members
YFR038W, SMARCA6, HELLS, LSH, PASG, DDM1, cha101