we found that ( i ) the core defines a strictly lens-specific element , ( ii ) an adjoining segment defines an element with a broad specificity with regard to cell type , ( iii ) these elements cooperate in cis within the delta 1-crystallin enhancer , ( iv ) the multimers of these elements complete with each other and with delta 1-crystallin and simian virus 40 enhancers in trans apparently without sequence specificity but in a fashion reflecting the strength of the enhancers , and ( v ) the enhancers in trans do not affect the expression of enhancer-free genes , thereby ruling out the possibility of competition for general transcription factors .
C0007634
cell type
C0086222
enhancer