SPL-RING finger found in E3 SUMO-protein ligase NSE2 and similar proteins
NSE2, also known as MMS21 homolog (MMS21) or non-structural maintenance of chromosomes element 2 homolog (Non-SMC element 2 homolog, NSMCE2), is an autosumoylating small ubiquitin-like modifier (SUMO) ligase required for the response to DNA damage. It regulates sumoylation and nuclear-to-cytoplasmic translocation of skeletal and heart muscle-specific variant of the alpha subunit of nascent polypeptide associated complex (skNAC)-Smyd1 in myogenesis. It is also required for resisting extrinsically induced genotoxic stress. Moreover, NSE2 together with its partner proteins SMC6 and SMC5 form a tight subcomplex of the structural maintenance of chromosomes SMC5-6 complex, which includes another two subcomplexes, NSE1-NSE3-NSE4 and NSE5-NSE6. SMC6 and NSE3 are sumoylated in an NSE2-dependent manner, but SMC5 and NSE1 are not. NSE2-dependent E3 SUMO ligase activity is required for efficient DNA repair, but not for SMC5-6 complex stability. NSE2 contains a RING variant known as a Siz/PIAS (protein inhibitor of activated signal transducer and activator of transcription)-like RING (SPL-RING) finger that is likely shared by the SP-RING type SUMO E3 ligases, such as PIAS family proteins. The SPL-RING finger is a variant of the RING finger, which lacks the second, fifth, and sixth zinc-binding residues of the consensus C3H2C3-/C3HC4-type RING fingers. It harbors only one Zn binding site and is required for the sumoylating activity.
Structure:2YU4; Homo sapiens NSE2 (Mms21) binds one Zinc2+ ion through its SPL-RING finger.
Comment:The SP-like RING (SPL-RING) domain of Mms21 proteins is likely shared by the SP-RING type SUMO E3 ligases, such as PIAS family proteins. These domains share sequence similarity with the RING domains of ubiquitin E3 ligases, but harbor only one Zn binding site.
Comment:The SPL-RING finger is a variant of RING finger, which lacks the second, fifth, and sixth zinc-binding residues of the consensus C3H2C3-/C3HC4-type RING fingers.
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