The five minigenes were designed as follows: (1) To construct the
lacZ reporter gene (see
Fig. 2A ) in vector I,
lacZ sequences were released from plasmid pKS-hsp-lacZ-pA obtained from Janet Rossant (Samuel Lunenfeld Research Institute of Mount Sinai Hospital, Toronto, Canada) by digestion with
BstEII and
XbaI, blunt ended and ligated into the
EcoRV site of vector 1
(Fig. 1) . (2) The human insulin cDNA clone was obtained from Graeme Bell (University of Chicago, Chicago, IL). The insulin cDNA was released by
EcoRI digestion and inserted into the
EcoRI site of the CPV2 plasmid
6 to make the αA-insulin minigene (see
Fig. 3A ), or blunt ended and inserted into the
SmaI site of vector 2 to make the δenαA-insulin minigene (see
Fig. 3B ). (3) The SV40 early region (approximately 2.7 kb) was released from the αA-cry-TAg plasmid
26 by
BamHI/
EcoRI digestion and inserted into a
BamHI/
EcoRI digest of vector 1 to make the δenαA-TAg minigene (see
Fig. 6 ). (4) To construct δenαA-E2F2, the human cDNA was isolated from CPV2-E2F2
11 by digestion with
EcoRI (blunt ended) and then
ClaI. The fragment was inserted into a
SmaI/
ClaI digest of vector 1 (see
Fig. 7 ). (5) The
dn-Spry2 cDNA clone was provided by Eisuke Nishida (Kyoto University, Kyoto, Japan).
27 The cDNA fragment was cut out by
BglII digestion, blunted with T4 DNA polymerase, and inserted into the
SmaI site of vector 2 (see
Fig. 8 ).