The domain goes by several names including SAD [1], SRA [2] and YDG [3]. It adopts a beta barrel, modified PUA-like, fold that is widely present in eukaryotic chromatin proteins and in bacteria [4]. Versions of this domain are known to bind hemi-m ...
The domain goes by several names including SAD [1], SRA [2] and YDG [3]. It adopts a beta barrel, modified PUA-like, fold that is widely present in eukaryotic chromatin proteins and in bacteria [4]. Versions of this domain are known to bind hemi-methylated CpG dinucleotides and also other 5mC containing dinucleotides. The domain binds DNA by flipping out the methylated cytosine base from the DNA double helix [5].The conserved tyrosine and aspartate residues and a glycine rich patch are critical for recognition of the flipped out base [4][5]. Mammalian UHRF1 that contains this domain plays an important role in maintenance of methylation at CpG dinucleotides by recruiting DNMT1 to hemimethylated sites associated with replication forks [2]. The SAD/SRA domain has been combined with other domains involved in the ubiquitin pathway on multiple occasions and such proteins link recognition of DNA methylation to chromatin-protein ubiquitination [4]. The domain is also found in species that lack DNA methylation, such as certain apicomplexans, suggestive of other DNA-binding modes or functions [4]. A highly derived and distinct version of the domain is also found in fungi where it is fused to AlkB-type 2OGFeDO domains [6]. In bacteria, the domain is usually fused or associated with restriction endonucleases, many of which target methylated or hemi-methylated DNA [4].
