Figure 1.

The Mandrill SAMHD1 Degron Comprises the N-Terminal and SAM Domains

(A) Schematic of the human and mandrill SAMHD1 and the tandem NLS-EGFP degron fusion protein construct employed in fluorescent degron assays. The C- and N-terminal degron regions in SAMHD1 are highlighted in green and magenta, respectively.

(B) Stable cell lines expressing either the mandrill (mnd) SAMHD1 1–114 degron (left) or human (hs) SAMHD1 600–626 degron (right) were transduced with increasing titers of particles carrying either SIV_smm Vpx (orange) or SIV_mnd-2 Vpx (blue) together with YFP. The level of degron (EGFP) and Vpx (YFP) expression was measured by flow cytometry. The upper panels are example FACS plots illustrating the populations of cells observed: untransduced cells (bottom right quadrant), cells transduced with a Vpx protein that can (top left quadrant) or cannot (top right quadrant) induce degradation of the degron reporter construct. The lower panels are quantification of degron reporter expression with increasing Vpx expression, demonstrating differential Vpx recognition of degron sequences.

(C) Quantification of degron reporter expression in stable cells lines expressing constructs containing the indicated N-terminal regions of SAMHD1_mnd after transduction with increasing amounts of SIV_mnd-2 Vpx; see also Figure S1.