Immunogen sequence: GPNPSTSFEP IKADPTGVLE LPKELSEIFD PTRECMSSEL LEELMSSEVF APLLRLSPPP GDHDYIYNLD ESEGVCD. E2F transcription factors are functionally regulated by binding to Rb p110, p107, and p130. E2F-4 is regulated by complex formation with Rb p110. E2