Bouchard B, Fuller B B, Vijayasaradhi S, Houghton A N
Memorial Sloan-Kettering Cancer Center, New York 10021.
J Exp Med. 1989 Jun 1;169(6):2029-42. doi: 10.1084/jem.169.6.2029.
A distinguishing characteristic of cells of the melanocyte lineage is the expression of the melanosomal enzyme tyrosinase that catalyzes the synthesis of the pigment melanin. A tyrosinase cDNA clone, designated BBTY-1, was isolated from a library constructed from the pigmented TA99+/CF21+ melanoma cell line SK-MEL-19. Expression of BBTY-1 in mouse L929 fibroblasts led to synthesis and expression of active tyrosinase, and, unexpectedly, to stable production of melanin. Melanin was synthesized and stored within membrane-bound vesicles in the cytoplasm of transfected fibroblasts. BBTY-1 detected a 2.4-kb mRNA transcript in nine of nine pigmented, tyrosinase-positive melanoma cell lines. Tyrosinase transcripts of the same size and abundance were detected in a subset (three of eight) of nonpigmented, tyrosinase-negative melanoma cell lines, suggesting that post-transcriptional events are important in regulating tyrosinase activity. Two melanocyte antigens, recognized by mAbs TA99 and CF21, that are specifically located within melanosomes and are coexpressed with tyrosinase activity, did not react with transfected mouse fibroblasts expressing human tyrosinase, supporting the conclusion that these antigenic determinants are distinct from the tyrosinase molecule coded for by BBTY-1.
黑素细胞谱系细胞的一个显著特征是黑素体酶酪氨酸酶的表达，该酶催化色素黑色素的合成。从由色素沉着的TA99+/CF21+黑色素瘤细胞系SK-MEL-19构建的文库中分离出一个酪氨酸酶cDNA克隆，命名为BBTY-1。BBTY-1在小鼠L929成纤维细胞中的表达导致了活性酪氨酸酶的合成与表达，并且意外地导致了黑色素的稳定产生。黑色素在转染的成纤维细胞细胞质中与膜结合的囊泡内合成并储存。BBTY-1在9个色素沉着、酪氨酸酶阳性的黑色素瘤细胞系中的9个中检测到一个2.4 kb的mRNA转录本。在一部分（8个中的3个）无色素、酪氨酸酶阴性的黑色素瘤细胞系中检测到相同大小和丰度的酪氨酸酶转录本，这表明转录后事件在调节酪氨酸酶活性中很重要。两种黑素细胞抗原，被单克隆抗体TA99和CF21识别，它们特异性地位于黑素体内并与酪氨酸酶活性共表达，但不与表达人酪氨酸酶的转染小鼠成纤维细胞发生反应，支持了这些抗原决定簇与BBTY-1编码的酪氨酸酶分子不同的结论。
