Identifying the N-terminus of SLX4Nter in HeLa KO30 cells

The project was aimed at identifying the N-terminus of a truncated form of SLX4 (termed SLX4Nter) in HeLa KO30 cells. The HeLa KO30 cell line comes from a clone of HeLa Flp-In T-Rex cells (termed FITo) obtained through a CRISPR-Cas9 approach using commercially available plasmids from Santa Cruz Biotechnology (sc-404395 and sc-404395-HDR). This allows the integration of an exogenous plasmid conferring Puromycin resistance at the endogenous SLX4 locus. Unexpectedly, this strategy allowed us to retrieve several Puromycin-resistant clones (including KO30) displaying a shorter form of endogenous SLX4 that is N-terminally truncated (SLX4Nter). To identify the proximal peptide of SLX4Nter, FITo and KO30 nuclear extracts were immunoprecipitated with anti-SLX4 antibodies and N-terminus of SLX4Nter was further identified by LC-MSMS analysis.