Lapeyre J N, Beattie W G, Dugaiczyk A, Vizard D, Becker F F
Gene. 1980 Sep;10(4):339-46. doi: 10.1016/0378-1119(80)90154-7.
The sequence of the 92 and 93 bp long, highly repetitive DNA fragments, isolated from EcoRI digested rat liver DNA, were determined. These fragments, designated 92 and 93, are found in equal abundance, 6.5 x 10(5) copies per haploid genome. J92 and J93 can be distinguished by their differential sensitivity to cleavage by HaeIII and HindIII, respectively, which cut the fragments at 75 and 57 bp from their mutually homologous 5'-ends. J92 and J93 are 38% and 35.4% G + C, respectively, and contain a disproportionate number of triplets complementary to stop codons in all reading frames. Three methylated sites were found in J92 while none could be detected in J93. The sequences around the m5C sites were 5'-Py-Py-m5C-G-Pu-Pu, except for one case where the second Py was replaced by an A. This site appeared to be hemimethylated. When J92 and J93 are placed in register from their mutually homologous 5'-ends, homology is 73% for the first 30 bp region and 63.5% for the total molecule. Thermal melting studies indicate sequence heterogeneity within J92 and J93 from substantial internal base mismatches. The sequences derived are therefore composite averages for the whole molecules. The Cot1/2 for the sequence was measured spectrophotometrically to be 2 x 10(-2) M/s on a DNA phosphorus basis and 2.15 x 10(-4) M/s on a mole fragment basis.
测定了从经EcoRI消化的大鼠肝脏DNA中分离出的长度为92和93bp的高度重复DNA片段的序列。这些片段分别命名为92和93，在单倍体基因组中以相等的丰度存在，每单倍体基因组有6.5×10⁵个拷贝。J92和J93可分别通过它们对HaeIII和HindIII切割的不同敏感性来区分，这两种酶分别从它们相互同源的5'-末端起在75bp和57bp处切割片段。J92和J93的G + C含量分别为38%和35.4%，并且在所有阅读框中都含有不成比例数量的与终止密码子互补的三联体。在J92中发现了三个甲基化位点，而在J93中未检测到。除了一个位点中第二个嘧啶被腺嘌呤取代外，m⁵C位点周围的序列为5'-Py-Py-m⁵C-G-Pu-Pu。这个位点似乎是半甲基化的。当J92和J93从它们相互同源的5'-末端对齐时，前30bp区域的同源性为73%，整个分子的同源性为63.5%。热变性研究表明，由于大量内部碱基错配，J92和J93内存在序列异质性。因此，推导得到的序列是整个分子的复合平均值。通过分光光度法在DNA磷基础上测得该序列的Cot1/2为2×10⁻²M/s，在摩尔片段基础上为2.15×10⁻⁴M/s。
