Department of Medical Biochemistry and Microbiology, Box 582 Biomedical Center, Uppsala University, Uppsala, Sweden.
Mol Microbiol. 2018 Jun;108(6):697-710. doi: 10.1111/mmi.13959. Epub 2018 Apr 25.
Bacteria can have multiple copies of a gene at separate locations on the same chromosome. Some of these gene families, including tuf (translation elongation factor EF-Tu) and rrl (ribosomal RNA), encode functions critically important for bacterial fitness. Genes within these families are known to evolve in concert using homologous recombination to transfer genetic information from one gene to another. This mechanism can counteract the detrimental effects of nucleotide sequence divergence over time. Whether such mechanisms can also protect against the potentially lethal effects of mobile genetic element insertion is not well understood. To address this we constructed two different length insertion cassettes to mimic mobile genetic elements and inserted these into various positions of the tuf and rrl genes. We measured rates of recombinational repair that removed the inserted cassette and studied the underlying mechanism. Our results indicate that homologous recombination can protect the tuf and rrl genes from inactivation by mobile genetic elements, but for insertions within shorter gene sequences the efficiency of repair is very low. Intriguingly, we found that physical distance separating genes on the chromosome directly affects the rate of recombinational repair suggesting that relative location will influence the ability of homologous recombination to maintain homogeneity.
细菌可以在同一染色体的不同位置拥有多个基因副本。这些基因家族中的一些，包括 tuf（翻译延伸因子 EF-Tu）和 rrl（核糖体 RNA），编码对细菌适应性至关重要的功能。这些家族中的基因被认为是通过同源重组协同进化的，即将遗传信息从一个基因转移到另一个基因。这种机制可以抵消核苷酸序列随时间推移产生的有害影响。然而，这种机制是否也能防止移动遗传元件插入的潜在致命影响，还不是很清楚。为了解决这个问题，我们构建了两个不同长度的插入盒，模拟移动遗传元件，并将它们插入到 tuf 和 rrl 基因的不同位置。我们测量了消除插入盒的重组修复率，并研究了其潜在机制。结果表明，同源重组可以保护 tuf 和 rrl 基因免受移动遗传元件的失活，但对于较短基因序列中的插入，修复效率非常低。有趣的是，我们发现染色体上基因之间的物理距离直接影响重组修复的速度，这表明相对位置会影响同源重组维持同源性的能力。
