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Expression of Alternatively Terminated Unusual Human Butyrylcholinesterase Messenger RNA Transcripts, Mapping to Chromosome 3q26-ter, in Nervous System Tumors¹

Department of Biological Chemistry, The Life Sciences Institute, The Hebrew University of Jerusalem, Israel 91904 [A. G., C. A. P., R. Z., J. L-H., H. S.], and Department of Obstetrics and Gynecology, The Edith Wolfson Medical Center, Holon 58100, Israel, The Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel [R. Z., H. Z.]

To study the molecular origin of the altered regulation of butyrylcholinesterase (BuChE) in nervous system tumors, BuChE complementary DNA (cDNA) sequences from human glioblastoma and neuroblastoma cDNA libraries were compared with BuChE cDNAs from normal fetal and adult tissues. A single 2.6-kilobase BuChE cDNA sequence was found in all normal tissues, whereas an additional alternatively terminated BuChE cDNA clone was found in both tumor libraries. The tumor-specific cDNA contained a 3', 0.7-kilobase nontranslatable extension, as well as several nucleotide alterations in the normal polyadenylation site. Single-base mutations in the coding region of this unusual BuChE cDNA infer two amino acid substitutions: Asp⁷⁰ Gly and Ser⁴²⁵ Pro. The Asp⁷⁰ Gly change has recently been implicated with "atypical" BuChE, which is deficient in its capacity to hydrolyze succinylcholine. The 3.6-kilobase mRNA was less abundant in RNA blot hybridization than the 2.6-kilobase mRNA, which is in agreement with the low ratios between the 3.6- and 2.6-kilobase BuChE cDNA clones in glioblastoma and neuroblastoma libraries. Furthermore, size fractionation and microinjection of glioblastoma polyadenylated RNA, followed by enzyme activity and selective inhibition measurements, demonstrated two peaks of functional BuChE mRNA, the heavier one probably reflecting the longer transcripts. Chromosomal mapping of the 0.7-kilobase 3' fragment by in situ hybridization localized it to a unique 3q26-ter position, where we recently found an inheritably amplified "silent" defective CHE gene in a family exposed to the cholinesterase inhibitor methyl parathion. Our findings confirm previous genetic linkage mapping of the functional CHE gene to the 3q26-ter position and demonstrate that extended functional mRNA transcripts encoding a BuChE form with two modified amino acids are produced from this gene in glioblastoma and neuroblastoma cells.

¹ This research was supported by the U.S. Army Medical Research and Development Command (contract DAMD 17-C-87-C-7169 to H. S.) and by the Research Fund at the Edith Wolfson Medical Center (to H. Z.). C. A. P. and J. L-H. were postdoctoral fellows of the Muscular Dystrophy Association of America and the Levi Eshkol Fund, respectively.

² Present address: Department of Pharmacology, The Washington University, St. Louis, MO.

³ To whom requests for reprints should be addressed.

Received 5/19/89. Revised 10/30/89.