Gene expression and prostate specificity of human prostatic acid phosphatase (PAP): evaluation by RNA blot analyses.

A fragment of a complementary DNA (cDNA) clone for human prostatic acid phosphatase (PAP) (EC 3.1.3.2.) was used to study the expression of corresponding mRNA in human tissues. The specificity of its expression in benign prostatic hyperplasia (BPH) and prostatic carcinoma tissues were indicated in RNA blot analyses. The PAPcDNA probe did not recognize any specific mRNAs in RNAs extracted from human liver cancer, lung cancer, pancreatic cancer, placenta, breast cancer cells (MCF-7), mononuclear blood cells or acute promyelocytic leukemia cells (HL-60), according to Northern blot analysis. mRNA for PAP was detected in the androgen-dependent human prostatic cancer cell line LNCaP, but not in the androgen-insensitive human prostatic cancer cell line PC-3. In contrast, lysosomal acid phosphatase (LAP) mRNA was detected in both of these human prostatic cancer cell lines. Our findings indicate a high specificity for the PAP gene in prostatic tissue. The mean abundance for the PAPmRNA expression was 0.26 for prostatic carcinoma samples (n = 11) and 0.46 for BPH samples (n = 8) according to slot-blot analysis. The differences observed between the different categories of prostatic tissue in PAPmRNA abundances call for additional studies on regulation of its expression.

Molecular cloning and sequence analysis of cDNA encoding human prostatic acid phosphatase.

lambda gt11 clones encoding human prostatic acid phosphatase (PAP) (EC 3.1.3.2) were isolated from human prostatic cDNA libraries by immunoscreening with polyclonal antisera. Sequence data obtained from several overlapping clones indicated that the composite cDNAs contained the complete coding region for PAP, which encodes a 354-residue protein with a calculated molecular mass of 41,126 Da. In the 5'-end, the cDNA codes for a signal peptide of 32 amino acids. Direct protein sequencing of the amino-terminus of the mature protein and its proteolytic fragments confirmed the identity of the predicted protein sequence. PAP has no apparent sequence homology to other known proteins. However, both the cDNA clones coding for human placental alkaline phosphatase and PAP have an alu-type repetitive sequence about 900 nucleotides downstream from the coding region in the 3'-untranslated region. Two of our cDNA clones differed from others at the 5'-ends. RNA blot analysis indicated mRNA of 3.3 kb. We are continuing to study whether acid phosphatases form a gene family as do alkaline phosphatases.