Greenberg J R, Perry R P
J Cell Biol. 1971 Sep;50(3):774-86. doi: 10.1083/jcb.50.3.774.
The relationship of the DNA sequences from which polyribosomal messenger RNA (mRNA) and heterogeneous nuclear RNA (NRNA) of mouse L cells are transcribed was investigated by means of hybridization kinetics and thermal denaturation of the hybrids. Hybridization was performed in formamide solutions at DNA excess. Under these conditions most of the hybridizing mRNA and NRNA react at values of D(o)t (DNA concentration multiplied by time) expected for RNA transcribed from the nonrepeated or rarely repeated fraction of the genome. However, a fraction of both mRNA and NRNA hybridize at values of D(o)t about 10,000 times lower, and therefore must be transcribed from highly redundant DNA sequences. The fraction of NRNA hybridizing to highly repeated sequences is about 1.7 times greater than the corresponding fraction of mRNA. The hybrids formed by the rapidly reacting fractions of both NRNA and mRNA melt over a narrow temperature range with a midpoint about 11 degrees C below that of native L cell DNA. This indicates that these hybrids consist of partially complementary sequences with approximately 11% mismatching of bases. Hybrids formed by the slowly reacting fraction of NRNA melt within 4 degrees -6 degrees C of native DNA, indicating very little, if any, mismatching of bases. Hybrids of the slowly reacting components of mRNA, formed under conditions of sufficiently low RNA input, have a high thermal stability, similar to that observed for hybrids of the slowly reacting NRNA component. However, when higher inputs of mRNA are used, hybrids are formed which have a strikingly lower thermal stability. This observation can be explained by assuming that there is sufficient similarity among the relatively rare DNA sequences coding for mRNA so that under hybridization conditions, in which these DNA sequences are not truly in excess, reversible hybrids exhibiting a considerable amount of mispairing are formed. The fact that a comparable phenomenon has not been observed for NRNA may mean that there is less similarity among the relatively rare DNA sequences coding for NRNA than there is among the rare sequences coding for mRNA.
通过杂交动力学和杂交体的热变性研究了小鼠L细胞多核糖体信使核糖核酸（mRNA）和不均一核RNA（NRNA）转录而来的DNA序列之间的关系。杂交在DNA过量的甲酰胺溶液中进行。在这些条件下，大多数杂交的mRNA和NRNA在基因组非重复或很少重复部分转录的RNA预期的D（o）t（DNA浓度乘以时间）值下发生反应。然而，一部分mRNA和NRNA在D（o）t值低约10000倍的情况下杂交，因此必定是从高度冗余的DNA序列转录而来。与高度重复序列杂交的NRNA部分比相应的mRNA部分大约大1.7倍。由NRNA和mRNA快速反应部分形成的杂交体在狭窄的温度范围内解链，中点比天然L细胞DNA的中点低约11℃。这表明这些杂交体由部分互补序列组成，碱基错配约11%。由NRNA缓慢反应部分形成的杂交体在天然DNA的4℃-6℃范围内解链，表明碱基错配极少（如果有的话）。在RNA输入量足够低的条件下形成的mRNA缓慢反应组分的杂交体具有高热稳定性，类似于观察到的NRNA缓慢反应组分的杂交体。然而，当使用更高的mRNA输入量时，形成的杂交体热稳定性显著降低。这一观察结果可以通过假设编码mRNA的相对罕见的DNA序列之间有足够的相似性来解释，以至于在杂交条件下，这些DNA序列并非真正过量时，会形成表现出相当数量错配的可逆杂交体。未在NRNA中观察到类似现象这一事实可能意味着编码NRNA的相对罕见的DNA序列之间的相似性比编码mRNA的罕见序列之间的相似性要小。
