MOLECULAR DESCRIPTION OF TELOMERIC HETEROCHROMATIN IN SECALE SPECIES
MOLECULAR DESCRIPTION OF TELOMERIC HETEROCHROMATIN IN SECALE SPECIES
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DOI：
10.1016/0092-8674(80)90529-2
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发表时间：
1980-01-01
期刊：
影响因子：
64.5
通讯作者：
FLAVELL, RB
中科院分区：
文献类型：
--
作者：
BEDBROOK, JR;JONES, J;FLAVELL, RB
本文描述了栽培黑麦中6个不同重复序列的物理性质、序列差异和染色体分布。所有这些序列主要位于构成端粒异染色质的区块内，通过Giemsa染色可以在该物种的所有7对染色体上观察到。小麦端粒异染色质占DNA的12-18%，而Sylvestre的端粒异染色质不到9%。四个特征重复可以解释大多数，如果不是全部，端粒异染色质DNA数量在密切相关的物种之间的差异。这4个重复序列在谷类链霉菌DNA中以高拷贝数存在，但在Silvestre链霉菌DNA中不能通过各种技术检测到。剩下的2个特征重复序列是2个黑麦种所共有的。两者都排列成简单的串联阵列，重复单元为120bp[碱基对]。主要的常见重复序列约占谷类链霉菌DNA的2.4%，次要重复序列占不到0.2%。主要的常见重复序列定位于黑麦染色体的间质部位和端粒部位。除了在S.Silvestre中不存在之外，这4个谷类作物特有的重复序列还有几个不同的物理特性。它们很复杂。每个序列都包含简单的亚重复序列，并夹杂着一个不相关的序列，而不包含亚重复序列。主要重复序列占谷类链霉菌DNA的5%-6%，重复序列长度为480bp，由一对.apprx组成。140个碱基与大约230个碱基的无关序列点缀在一起。另一个谷类链霉菌重复序列占总DNA的2-3%，其重复单位为610个碱基，由110个碱基的三联体和一个280个碱基无关的序列组成。根据体外形成的双链体的热稳定性判断，480和610个碱基的重复家族在序列上都比在这两个黑麦中发现的重复家族更同质。剩下的两个谷类链霉菌特有的重复序列与次要的120个碱基的共同重复序列有关。其中一个重复单位为356bp，由两个120bp的亚重复序列组成，其间散布着116bp的无关序列。另一个是630bp的重复序列，它有一个270 bp的序列，其中散布着120个bp的亚重复序列中的3个。每个谷类链霉菌特有的重复序列可能是通过将DNA元件插入到简单重复序列阵列中，然后扩增包含插入序列的阵列部分而进化而来的。
The physical properties, sequence divergence and chromosomal distribution of 6 different repeated sequences in S. cereale (cultivated rye) are described. All these sequences are located predominantly within blocks of constitutive telomeric heterochromatin which can be observed on all 7 pairs of chromosomes of this species by Giemsa staining. The telomeric heterochromatin accounts for 12-18% of the DNA of S. cereale but less than 9% in S. sylvestre. Four of the characterized repeats account for most, if not all, of this difference in telomeric heterochromatin DNA amount between the closely related species. These 4 repeats are present in high copy number in S. cereale DNA but are not detected by various techniques in S. silvestre DNA. The remaining 2 characterized repeats are common to the 2 Secale spp. Both are arranged in simple tandem arrays with a repeating unit of 120 bp [base pairs]. The major common repeat represents approximately 2.4% of S. cereale DNA and the minor one represents less than 0.2%. The major common repeat is localized in interstitial sites in Secale chromosomes and in the telomeric sites. The 4 S. cereale-specific repeats have several distinguishing physical properties beside their absence in S. silvestre. They are complex. Each contains simple subrepeats interspersed with an unrelated sequence without subrepeats. The major repeat, constituting 5-6% of S. cereale DNA, has a repeat length of 480 bp consisting of a doublet of .apprx. 140 bp interspersed with an unrelated sequence of approximately 230 bp. Another S. cereale repeat representing 2-3% of the total DNA has a repeat unit of 610 bp consisting of a triplet of 110 bp units interspersed with a 280 bp unrelated sequence. Both the 480 and 610 bp repeat families are more homogeneous in sequence, as judged by the thermal stability of duplexes formed in vitro, than the repeat families found in both Secale spp. The 2 remaining S. cereale-specific repeats are related to the minor 120 bp common repeat. One had a repeat unit of 356 bp and consists of 2 of the 120 bp subrepeats interspersed with an unrelated sequence of 116 bp. The other, a 630 bp repeat, has a 270 bp sequence interspersed with 3 of the 120 bp subrepeats. Each of the S. cereale-specific repeats may have evolved by the insertion of DNA elements into an array of simple repeats followed by amplification of the portion of the array containing the inserted sequence.