FIGURE 2.

Identification of phosphorylation sites in c-Myb isolated from stressed cells by mass spectrometry. A, protein sequence of mouse c-Myb protein. The shaded residues were identified in the tryptic peptides from the nonSUMOylated form of c-Myb isolated from untreated cells (c-Myb@37°C) and nonSUMOylated c-Myb (c-Myb@43°C) and SUMOylated c-Myb (S2₁-c-Myb@43°C) from cells treated with hyperthermia. Total protein coverage is shown for every sample analyzed. Phosphorylation sites identified in analyzed samples are marked in red. Three new phosphorylation sites Thr²⁰⁸, Ser⁴⁴⁴, and Thr⁴⁸⁶ were identified in c-Myb isolated from stressed cells. SUMOylation motifs ⁴⁹⁸IKRE⁵⁰¹ and ⁵²²IKQE⁵²⁵ are underlined. B, conservation of c-Myb protein sequences (459–509 amino acids, murine numbering). Phosphorylation site Thr⁴⁸⁶ is located amino-terminally to SUMOylation site Lys⁴⁹⁹. The SUMOylation motif IKRE is underlined. Identity and similarity of the c-Myb sequences between mouse and other species are presented in the table.