Judy and Bernard Briskin Center for Multiple Myeloma Research, City of Hope, Duarte, CA, U.S.A.
Beckman Research Institute of the City of Hope, Duarte, CA, U.S.A.
Cancer Genomics Proteomics. 2024 May-Jun;21(3):238-251. doi: 10.21873/cgp.20443.
BACKGROUND/AIM: Dynamic DNA sequences (i.e. sequences capable of forming hairpins, G-quadruplexes, i-motifs, and triple helices) can cause replication stress and associated mutations. One example of such a sequence occurs in the RACK7 gene in human DNA. Since this sequence forms i-motif structures at neutral pH that cause replication stress and result in spontaneous deletions in prostate cancer cells, our initial aim was to determine its potential utility as a biomarker of prostate cancer.
We cloned and sequenced the region in RACK7 where i-motif deletions often occur in DNA obtained from eight individuals. Expressed prostatic secretions were obtained from three individuals with a positive biopsy for prostate cancer and two with individuals with a negative biopsy for prostate cancer. Peripheral blood specimens were obtained from two control healthy bone marrow donors and a marrow specimen was obtained from a third healthy marrow donor. Follow-up computer searches of the genomes of 74 mammalian species available at the NCBI ftp site or frequencies of 6 dynamic sequences known to produce mutations or replication stress using a program written in Mathematica were subsequently performed.
Deletions were found in RACK7 in specimens from both older normal adults, as well as specimens from older patients with cancer, but not in the youngest normal adult. The deletions appeared to show a weak trend to increasing frequency with patient age. This suggested that endogenous mutations associated with dynamic sequences might accumulate during aging and might serve as biomarkers of biological age rather than direct biomarkers of cancer. To test that hypothesis, we asked whether or not the genomic frequencies of several dynamic sequences known to produce replication stress or mutations in human DNA were inversely correlated with maximum lifespan in mammals.
Our results confirm this correlation for six dynamic sequences in 74 mammalian genomes studied, thereby suggesting that spontaneously induced replication stress and mutations linked to dynamic sequence frequency may limit lifespan by limiting genome stability.
背景/目的：动态 DNA 序列（即能够形成发夹、G-四链体、i- motif 和三螺旋的序列）会引起复制应激和相关突变。这种序列的一个例子存在于人类 DNA 中的 RACK7 基因中。由于该序列在中性 pH 下形成 i-motif 结构，导致复制应激，并导致前列腺癌细胞自发缺失，我们最初的目的是确定其作为前列腺癌生物标志物的潜在用途。
我们克隆并测序了 RACK7 中经常发生 i-motif 缺失的区域的 DNA，该 DNA 来自 8 个人。从 3 位前列腺癌阳性活检患者、2 位前列腺癌阴性活检患者中获得了前列腺分泌物。从 2 位对照健康骨髓供体中获得了外周血标本，从第 3 位健康骨髓供体中获得了骨髓标本。随后在 NCBI ftp 站点上可用的 74 种哺乳动物基因组中进行了后续计算机搜索，或者使用 Mathematica 编写的程序对已知产生突变或复制应激的 6 个动态序列的频率进行了搜索。
在年龄较大的正常成年人以及年龄较大的癌症患者的标本中发现了 RACK7 的缺失，但在年龄最小的正常成年人中没有发现。缺失似乎显示出与患者年龄相关的微弱增加趋势。这表明与动态序列相关的内源性突变可能会随着年龄的增长而积累，并可能作为生物年龄的生物标志物，而不是癌症的直接生物标志物。为了验证这一假设，我们询问了已知在人类 DNA 中产生复制应激或突变的几种动态序列的基因组频率是否与哺乳动物的最大寿命呈负相关。
我们的研究结果证实了这一假说，即 74 种哺乳动物基因组中的 6 种动态序列的相关性，从而表明与动态序列频率相关的自发诱导的复制应激和突变可能通过限制基因组稳定性来限制寿命。
