Fig. 1

Illustration of CAPERα interactions and structure. a Interactions of CAPERα with DCAF15 mediated by E7820 via a molecular glue mechanism leads to polyubiquitinylation (ubi) of the former by cullin-RING ubiquitin ligase 4 (CRL4) and subsequent proteasomal degradation [12, 13]. This impedes the interaction between CAPERα and activator protein-1 (AP-1) as well as estrogen receptor (ER) [14], both of which represent plausible links to the regulation of integrin α2 expression [15, 16]. b Domain structure of CAPERα adapted from Jung et al. showing a serine/arginine-rich domain (SR) and three RNA-recognition motifs (RRM1–3) [14, 17]. The interaction sites with the c-Jun domain of activator protein 1 (AP-1), with oestrogen receptor α and β (ER) and with activating signal co-integrator 2 (ASC-2) are indicated [14]. Purple labels indicate mutations found in E7820 resistant cell lines [12, 17]. Blue labels show the molecular interactions of specific amino acids with E7820 [10]. c Structure of different CAPERα isoforms. The variable n-terminal domain (yellow) may be entirely deleted (ΔM1-C157), contain a substitution of an alternate 25 amino acids for the initial 33 n-terminal amino acids (M1-K33sub25), lack 12 amino acids from serine 110 to serine 121 (ΔS110-S121), or lack serine 121 only (ΔS121). The MII-2 domain (red) may be completely (ΔG366-I397) or partly (ΔE392-I397) missing. The murine (MM) and human (HS) isoforms (iso) that contain each of these features are indicated