Hyaluronan binding motifs of USP17 and SDS3 exhibit anti-tumor activity.
BACKGROUND
We previously reported that the USP17 deubiquitinating enzyme having hyaluronan binding motifs (HABMs) interacts with human SDS3 (suppressor of defective silencing 3) and specifically deubiquitinates Lys-63 branched polyubiquitination of SDS3 resulting in negative regulation of histone deacetylase (HDAC) activity in cancer cells. Furthermore, USP17 and SDS3 mutually interact with each other to block cell proliferation in HeLa cells but the mechanism for this inhibition in cell proliferation is not known. We wished to investigate whether the HABMs of USP17 were responsible for tumor suppression activity.


RESULTS
Similarly to USP17, we have identified that SDS3 also has three consecutive HABMs and shows direct binding with hyaluronan (HA) using cetylpyridinium chloride (CPC) assay. Additionally, HA oligosaccharides (6-18 sugar units) competitively block binding of endogenous HA polymer to HA binding proteins. Thus, administration of HA oligosaccharides antagonizes the interaction between HA and USP17 or SDS3. Interestingly, HABMs deleted USP17 showed lesser interaction with SDS3 but retain its deubiquitinating activity towards SDS3. The deletion of HABMs of USP17 could not alter its functional regulation on SDS3-associated HDAC activity. Furthermore, to explore whether HABMs in USP17 and SDS3 are responsible for the inhibition of cell proliferation, we investigated the effect of USP17 and SDS3-lacking HABMs on cell proliferation by soft agar, apoptosis, cell migration and cell proliferation assays.


CONCLUSIONS
Our results have demonstrated that these HABMs in USP17 and its substrate SDS3 are mainly involved in the inhibition of anchorage-independent tumor growth.
Department of Biomedical Science, CHA University, CHA General Hospital, Gyeonggi-Do, Republic of Korea.
Suresh
S
Ramakrishna
Bharathi
B
Suresh
Su-Mi
SM
Bae
Woong-Shick
WS
Ahn
Key-Hwan
KH
Lim
Kwang-Hyun
KH
Baek
D000595:Amino Acid Sequence; D001483:Base Sequence; D049109:Cell Proliferation; D010450:Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism*; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
D012097:Repressor Proteins; C576731:SUDS3 protein, human; D006820:Hyaluronic Acid; D010450:Endopeptidases; C484854:USP17L2 protein, human