英语翻译Patterns and inheritance of methylationDense methylation

英语翻译
Patterns and inheritance of methylation
Dense methylation at all Cs is observed in sequences
modified by RIP and MIP,where the respective methylation
signals appear to be an altered sequence composition
[19] or paired DNA segments longer than 400 bp [17··].
Although most methylation in plants is present in
symmetrical CG and CNG nucleotide groups (N standing
for A,G,C or T),methylation of nonsymmetrical Cs has
been observed in both foreign sequences (transgenes
and TEs) and endogenous genes (reviewed in [10]).
The heavy methylation incurred by nonsymmetrical
Cs around the transcription start site and in most of
the transcribed region of weak epialleles of the single
copy endogenous gene SUPERMAN [20·] indicates that
this pattern of methylation does not require extensive
DNA–DNA pairing or a readily recognizable foreign DNA
sequence,such as a TE or a repeat of appreciable
length.The SUPERMAN gene does,however,contain
a 50 bp run of the dinucleotide C[A/T] that comprises
the transcription start site.This short microsatellite might
attract methylation that decreases expression.
The Ascobolus methyl transferase (MTase) gene,Masc1,
responsible for de novo methylation during MIP of all
Cs in paired DNA regions,encodes an enzyme unlike
known eukaryotic MTases [17··],which preferentially
modify hemimethylated DNA and therefore perform primarily
a maintenance methylation function.Maintenance
methylation is not perturbed in masc1 mutants,so a
second novel MTase that perpetuates methylation of
nonsymmetrical Cs must also be present in Ascobolus [16].
Further characterization of the three types of MTases
discovered so far is necessary to determine whether
MTases with similar activities and substrate specificities
are present in plants [10]
Position effects on transgene expression
In yeast and Drosophila,silencing resulting from position
effects can occur at telomeres and centromeres,which
are heterochromatic in Drosophila [21,22].These silencing
phenomena are not identical:telomeric position effect variegation
(PEV) in Drosophila is insensitive to suppressors
and enhancers of centromeric PEV [23].In addition to
centromeres and telomeres,most higher plant genomes
contain substantial amounts of intercalary heterochromatin
and repetitive DNA,which can be used as landmarks
to evaluate regions associated with transgene silencing.
Position effects involving one or more transgene loci can
be studied in various ways (Figure 1).

Patterns and inheritance of methylation
模式和继承的甲基化
Dense methylation at all Cs is observed in sequences
在浓密的甲基化Cs中观察序列
modified by RIP and MIP,where the respective methylation
被RIP和MIP,那里的各自的甲基化
signals appear to be an altered sequence composition
信号序列改变出现的作文
[19] or paired DNA segments longer than 400 bp [17··].
或一对DNA片段超过400 bp
Although most methylation in plants is present in
虽然大多数甲基化中所呈现的植物
symmetrical CG and CNG nucleotide groups (N standing
对称的CG、CNG核苷酸团体(N站着
for A,G,C or T),methylation of nonsymmetrical Cs has
一、G、C、T)的非均匀储运甲基化
been observed in both foreign sequences (transgenes
无论是国外见于外源基因序列(
and TEs) and endogenous genes (reviewed in [10]).
和下和内源性基因(了)[10]所聚集的相当.
The heavy methylation incurred by nonsymmetrical
沉重的甲基化,费用由非均匀
Cs around the transcription start site and in most of
Cs在转录起始点也最多
the transcribed region of weak epialleles of the single
弱epialleles转录地区的单
copy endogenous gene SUPERMAN [20·] indicates that
复制内源性基因超人[20·]表明
this pattern of methylation does not require extensive
这个模式不需要很多的甲基化
DNA–DNA pairing or a readily recognizable foreign DNA
DNA-DNA或容易辨认配对的外来DNA
sequence,such as a TE or a repeat of appreciable
序列,如一特或重复欣赏的
length.The SUPERMAN gene does,however,contain
长度.“超人”,不过,含有基因确实
a 50 bp run of the dinucleotide C[A/T] that comprises
一个50 bp运行的二[C]/ T组成的
the transcription start site.This short microsatellite might
转录起始点.这篇简短的微卫星可能
attract methylation that decreases expression.
吸引甲基化,从而减少的表情.
The Ascobolus methyl transferase (MTase) gene,Masc1,
Ascobolus甲基转移酶的基因,Masc1(MTase),
responsible for de novo methylation during MIP of all
负责德novo甲基化在MIP
Cs in paired DNA regions,encodes an enzyme unlike
在DNA配对Cs地区,编码一种不像
known eukaryotic MTases [17··],which preferentially
已知的真核MTases[17··],优先
modify hemimethylated DNA and therefore perform primarily
修改hemimethylated DNA和以此完成为主
a maintenance methylation function.Maintenance
维修甲基化功能.维护
methylation is not perturbed in masc1 mutants,so a
甲基化是不摄动,所以在masc1突变体
second novel MTase that perpetuates methylation of
第二部小说MTase甲基化,使特定的
nonsymmetrical Cs must also be present in Ascobolus [16].
非均匀Cs也必须出现在Ascobolus[16].
Further characterization of the three types of MTases
进一步的表征MTases的三种类型
discovered so far is necessary to determine whether
到目前为止发现需要确定
MTases with similar activities and substrate specificities
MTases特异性和基材与类似的活动
are present in plants [10]
出现在植物中
Position effects on transgene expression
位置影响表达.水平上
In yeast and Drosophila,silencing resulting from position
在酵母和果蝇、静音造成的位置
effects can occur at telomeres and centromeres,which
影响可能会发生在端粒,每条,
are heterochromatic in Drosophila [21,22].These silencing
是在heterochromatic果蝇[21、22].这些沉默
phenomena are not identical:telomeric position effect variegation
现象不是相同的:端粒的位置效应色浆流动性
(PEV) in Drosophila is insensitive to suppressors
(张道惠夫人将洋芋引入石门坎果蝇)不消除器
and enhancers of centromeric PEV [23].In addition to
centromeric张道惠夫人将洋芋引入石门坎的错误,(23).除了
centromeres and telomeres,most higher plant genomes
每条和端粒,大多数高等植物基因组
contain substantial amounts of intercalary heterochromatin
异的形式富含大量添加日
and repetitive DNA,which can be used as landmarks
和重复DNA,可作为陆标
to evaluate regions associated with transgene silencing.
有关区域评价转基因沉默.
Position effects involving one or more transgene loci can
包括一个或多个位置的影响基因位点的转基因
be studied in various ways (Figure 1).
以各种不同的方式研究(图1).