Regulation of apoptosis at various stages of differentiation plays an important 
role in spermatogenesis. Therefore, the identification and characterisation of 
highly expressed genes in the testis that are involved in apoptosis is of great 
value to delineate the mechanism of spermatogenesis. Here, we reported that 
Fank1, a novel gene highly expressed in testis, functioned as an anti-apoptotic 
protein that activated the activator protein 1 (AP-1) pathway. We found that 
Jab1 (Jun activation domain-binding protein 1), a co-activator of AP-1, 
specifically interacted with Fank1. Reporter analyses showed that Fank1 
activated AP-1 pathway in a Jab1-dependent manner. Fank1 overexpression also 
increased the expression and activation of endogenous c-Jun. Further study 
showed that Fank1 inhibited cell apoptosis by upregulating and activating 
endogenous c-Jun and its downstream target, Bcl-3. This process was shown to be 
Jab1 dependent. Taken together, our results indicated that by interacting with 
Jab1, Fank1 could suppress cell apoptosis by activating the AP-1-induced 
anti-apoptotic pathway.