title: A novel pocket in 14-3-3epsilon is required to mediate specific complex formation with cdc25C and to inhibit cell cycle progression upon activation of checkpoint pathways.
abstract: Mitotic progression requires the activity of the dual specificity phosphatase, cdc25C. Cdc25C function is inhibited by complex formation with two 14-3-3 isoforms, 14-3-3epsilon and 14-3-3gamma. To understand the molecular basis of specific complex formation between 14-3-3 proteins and their ligands, chimeric 14-3-3 proteins were tested for their ability to form a complex with cdc25C in vivo. Specific complex formation between cdc25C and 14-3-3epsilon in vivo requires a phenylalanine residue at position 135 (F135) in 14-3-3epsilon. Mutation of this residue to the corresponding residue present in other 14-3-3 isoforms (F135V) leads to reduced binding to cdc25C and a decrease in the ability to inhibit cdc25C function in vivo. Similarly, F135V failed to rescue the incomplete S phase and the G2 DNA damage checkpoint defects observed in cells lacking 14-3-3epsilon. A comparative analysis of the 14-3-3 structures present in the database suggested that the F135 in 14-3-3epsilon was required to maintain the integrity of a pocket that might be involved in secondary interactions with cdc25C. These results suggest that the specificity of the 14-3-3 ligand interaction may be dependent on structural motifs present in the individual 14-3-3 isoforms.
authors.affiliation: KS215, Advanced Centre for Treatment Research and Education in Cancer (ACTREC), Tata Memorial Centre, Kharghar Node, Navi Mumbai 410210, India.
authors.forename: Elphine
authors.initials: E
authors.lastname: Telles
authors.forename: Amol S
authors.initials: AS
authors.lastname: Hosing
authors.forename: Samrat T
authors.initials: ST
authors.lastname: Kundu
authors.forename: Prasanna
authors.initials: P
authors.lastname: Venkatraman
authors.forename: Sorab N
authors.initials: SN
authors.lastname: Dalal