Maric S C, Crozat A, Louhimo J, Knuutila S, Jänne O A
Department of Physiology, University of Helsinki, Finland.
Cytogenet Cell Genet. 1995;70(3-4):195-9. doi: 10.1159/000134032.
S-adenosylmethionine decarboxylase (AdoMet-DC) is a key enzyme in polyamine biosynthesis. The human genome contains at least two loci for the AdoMetDC gene (AMD), one of which (AMD1) has previously been mapped to chromosome 6 and the other (AMD2) to the X chromosome. The locus on chromosome 6 is the transcriptionally active gene. We now report characterization of the AMD2 locus (GenBank Accession No. U02035) on the X chromosome, which contains sequences that cross-hybridize with human AdoMetDC cDNA. This DNA lacks all of the introns present in AMD1 and has numerous mutations in the protein-coding region. Its overall nucleotide sequence identity with AdoMetDC cDNA is about 90%. AMD2 is therefore a processed pseudogene, which, because of multiple mutations, cannot be translated to an active AdoMetDC enzyme, even if it were transcribed. Chromosomal loci for human AMD sequences were determined by in situ hybridization to metaphase chromosomes, with genomic DNAs from the active gene and the pseudogene loci as probes. AMD1 was localized to chromosome region 6q21-->q22 and AMD2 to band Xq28.
S-腺苷甲硫氨酸脱羧酶（AdoMet-DC）是多胺生物合成中的关键酶。人类基因组中至少有两个AdoMetDC基因（AMD）位点，其中一个（AMD1）先前已定位到6号染色体，另一个（AMD2）定位到X染色体。6号染色体上的位点是转录活性基因。我们现在报告对X染色体上AMD2位点（GenBank登录号U02035）的特征描述，该位点包含与人类AdoMetDC cDNA交叉杂交的序列。该DNA缺乏AMD1中存在的所有内含子，并且在蛋白质编码区有许多突变。其与AdoMetDC cDNA的总体核苷酸序列同一性约为90%。因此，AMD2是一个加工假基因，由于存在多个突变，即使它被转录，也无法翻译成活性AdoMetDC酶。通过用来自活性基因和假基因位点的基因组DNA作为探针与中期染色体进行原位杂交，确定了人类AMD序列的染色体位点。AMD1定位于染色体区域6q21→q22，AMD2定位于Xq28带。
