These results suggest that a family of distinct pro- 
teins sharing a common structural motif may regu- 
late the diverse transcriptional effects mediated by 
CREs. Dr. Leiden's laboratory is studying the inter- 
action of CREB-2 with other recently described 
CRE-binding proteins and testing the role of spe- 
^ cific amino acids in the basic domains of CRE- and 
TRE-binding proteins in determining the specificity 
of DNA binding of these two families of transcrip- 
tional regulators. 
II. Structure, Function, and Expression of the Car- 
diac Troponin C Gene. 
Cardiac troponin C (cTnC) is the calcium-binding 
subunit of the myofibrillar thin filament that regu- 
lates excitation-contraction coupling in cardiac 
muscle. Dr. Leiden's laboratory has utilized a novel 
polymerase chain reaction-cloning procedure to 
isolate cDNA clones encoding murine cTnC. Mu- 
rine cTnC is a l6l-amino acid polypeptide that has 
been highly conserved during evolution. Dr. 
Leiden's laboratory has shown that the cTnC gene 
is a member of a multigene family and is expressed 
in murine cardiac and slow skeletal muscle but not 
in fast skeletal muscle, nor in neonatal or adult 
brain, kidney, lung, liver, or testis. In addition, al- 
though the cTnC gene is not expressed in murine 
C2C12 myoblasts, differentiation of these cells into 
myotubes was shown to result in a dramatic induc- 
tion of cTnC gene expression. A full-length cTnC 
genomic clone was isolated from a murine genomic 
library. The cTnC gene is 3.4 kb long and is com- 
posed of six exons. Analysis of the 5'-flanking re- 
PUBLICATIONS 
gion of the gene revealed the presence of a consen- 
sus TATA box 24 bp 5' of the transcription start site. 
However, despite the finding that the gene is ex- 
pressed only in cardiac and slow skeletal muscle, it 
lacks the previously described CArG and M-CAT se- 
quence motifs, which are involved in regulating the 
expression of a number of other myofibrillar genes. 
These results demonstrate that cTnC gene expres- 
sion is developmentally regulated and lineage spe- 
cific. Dr. Leiden and his colleagues have also de- 
fined an in vitro system, the C2C12 myoblast, 
which can be used in transfection studies designed 
to identify the cis-acting regulatory elements and 
trans-acting factors that control cTnC gene expres- 
sion during myocyte diffierentiation. It is hoped that 
such studies will lead to the identification of novel 
cardiac-specific transcriptional regulatory factors. 
Dr. Leiden's laboratory has also recently designed 
a prokaryotic expression system that has allowed 
the production and purification of large amounts of 
recombinant cTnC protein. This purified recombi- 
nant protein has been used to produce monoclonal 
antibodies specific for cTnC. Because cTnC is a rela- 
tively small and abundant protein that is expressed 
in a cardiac-specific fashion, an ELISA assay based 
on these antibody reagents may be useful in the 
early diagnosis of patients suffering from acute 
myocardial infarction. A clinical trial of these anti- 
bodies is in progress. 
Dr. Leiden is also Assistant Professor of Internal 
Medicine and of Microbiology and Immunology at 
the University of Michigan Medical School. 
Books and Chapters of Books 
Leiden, J., and Kornbluth, J. 1989. The role of class I HLA expression in NK target susceptibility: expression 
of a transfected cloned human HLA-A2 gene does not alter the NK target susceptibility of K562 cells. In 
Natural Killer Cells and Host Defense (Ades, E.W, and Lopez, C, Eds.). Basel: Karger, pp 198-206. 
Articles 
Gottesdiener, K.M., Karpinski, B.A., Lindsten, T, Strominger, J.L., Jones, N.H., Thompson, C.B. , and Leiden, 
J.M. 1988. Isolation and structural characterization of the human 4F2 heavy-chain gene, an inducible gene 
involved in T-lymphocyte activation. Mol Cell Biol 8:3809-3819. 
June, C.H., Jackson, K.M., Ledbetter, J.A., Leiden, J.M. , Lindsten, T, and Thompson, C.B. 1989. Two distinct 
mechanisms of interleukin-2 gene expression in human T lymphocytes. J Autoimmun 2(Suppl):55-65. 
Karpinski, B.A. , Yang, L.-H., Cacheris, P., Morle, G.D. , and Leiden, J.M. 1989. The first intron of the 4F2 heavy- 
chain gene contains a transcriptional enhancer element that binds multiple nuclear proteins. Mol Cell 
Biol 9:2588-2597. 
Leiden, J.M., Karpinski, B.A. , Gottschalk, L. , and Kornbluth, J. 1989. Susceptibility to natural killer cell-medi- 
ated cytolysis is independent of the level of target cell class I HLA expression. J Immunol 142:2140-2147. 
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