Nucleic Acids Research, Vol 24, Issue 4 602-610, Copyright © 1996 by Oxford University Press
I Barash, M Nathan, R Kari, N Ilan, M Shani and DR Hurwitz
Two new beta-lactoglobulin (BLG)/human serum albumin (HSA) hybrid gene
vectors were constructed and tested for expression in COS-7 cells and in
transgenic mice. The HSA sequences were inserted between the second and
sixth BLG exons. Transient transfection experiments with these vectors as
well as a series of additional vectors with either the BLG 5'- or 3'-
intragenic sequences revealed that sequences within BLG exon 1/intron
1/exon 2 abrogated BLG- directed HSA expression in vitro, regardless of the
presence of HSA introns or the origin of the 3' polyadenylation signal. In
contrast, the same BLG expression cassette enabled the efficient expression
of HSA cDNA or minigene in the mammary gland of transgenic mice with
subsequent secretion of the corresponding protein into the milk of 56 and
82%, respectively of the mouse strains at levels up to 0.3 mg/ml. Previous
attempts to express HSA cDNA inserted into exon 1 of the BLG gene had
failed [Shani,M., Barash,I., Nathan,M., Ricca,G., Searfoss,G.H., Dekel,I.,
Faerman,A., Givol,D. and Hurwitz,D.R. (1992) Transgenic Res. 1, 195- 208].
The new BLG expression cassette conferred more stringent tissue specific
expression than previously described BLG/HSA constructs [Barash,I,
Faerman,A., Ratovitsky,T, Puzis,R., Nathan,M., Hurwitz,D.R. and Shani, M.
(1994) Transgenic Res. 3, 141-151]. However, it was not able to insulate
the transgenes from the surrounding host DNA sequences and did not result
in copy number dependent expression in transgenics. Together, the in vitro
and in vivo results suggest both positive and negative regulatory elements
within the BLG intragenic sequences evaluated. The new BLG construct
represents an extremely valuable vector for the efficient expression of
cDNAs in the mammary gland of transgenic animals.
ARTICLES
Elements within the beta-lactoglobulin gene inhibit expression of human serum albumin cDNA and minigenes in transfected cells but rescue their expression in the mammary gland of transgenic mice
Institute of Animal Science, Volcani Center, Bet Dagan 50250, Israel.
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