Definition: In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.
Input: In contrast to the p16 - mediated G1 block , G1 arrest mediated by the cdk inhibitors p21Cip1 or p27Kip1 cannot be bypassed either by inactivation of pRb or overexpression of E2F family members .
Output:
E2F family members