Figure 4.

Regulation of Jun amino-terminal kinase signalling by Plenty of SH3s. (A) Time-course analysis of Jun amino-terminal kinase (JNK) phosphorylation after peptidoglycan stimulation of S2 cells transfected with Plenty of SH3s doublestranded RNA (POSH dsRNA), POSH or POSH^mR DNA. Peptidoglycan-induced JNK activation is delayed and sustained in cells treated with POSH dsRNA. In contrast, JNK activation is rapidly terminated when wild-type POSH is overexpressed, whereas the activated JNK persists for a longer time period when POSH^mR is overexpressed. LPS, lipopolysaccharide; phos-JNK, phorphorylated JNK. (B) Real-time PCR analysis showing the time-course analysis of puckered (puc) expression. Expression level of puc, a target of the JNK pathway, is rapidly reduced in flies overexpressing POSH, but is sustained in those overexpressing POSH^mR, which suggests that RING-defective POSH has a dominant-negative effect on JNK signalling activated by infection.