Brown Petrice W, Hwang KeumSil, Schlegel Peter N, Morris Patricia L
Center for Biomedical Research, Population Council, New York, NY 10065, USA.
Hum Reprod. 2008 Dec;23(12):2850-7. doi: 10.1093/humrep/den300. Epub 2008 Aug 10.
Post-transcriptional modification by SUMOylation is involved in numerous cellular processes including human spermatogenesis. For human male meiosis, we previously showed that the small ubiquitin-related modifier-1 (SUMO-1) protein localizes to chromatin axes in early pachytene spermatocytes, then to kinetochores as meiosis progresses. Here, we delineate possible functional roles based on subcellular localization for SUMO-1 and SUMO-2/3.
Western and immunoprecipitation analyses were conducted on proteins isolated from the testis of two normal adult fertile men. Combinatorial immunofluorescence and chromosome-specific fluorescence in situ hybridization analyses were performed on male meiocytes obtained during testicular biopsy from four patients undergoing testicular sperm extraction for assisted reproduction technologies.
The synaptonemal complex (SC) and SC proteins (SCP)-1 and SCP2, but not SCP3, are SUMOylated by SUMO-1 during the pachytene substage. Likewise, two distinct localization patterns for SUMO-1 are identified: a linear pattern co-localized with autosomal SCs and isolated SUMO-1 near the centromeric heterochromatin of chromosomes 9 and 1. In contrast to SUMO-1, which is not detectable prior to pachytene in normal tissue, SUMO-2/3 is identified as early as leptotene and zygotene and in some, but not all, pachytene cells; no linear patterns were detected. Similar to SUMO-1, SUMO-2/3 localizes in two predominant subnuclear patterns: a single, dense signal near the centromere of human chromosome 9 and small, individual foci co-localized with autosomal centromeres.
Our data suggest that SUMO-1 may be involved in maintenance and/or protection of the autosomal SC. SUMO-2/3, though expressed similarly, may function separately and independently during pachytene in men.
小泛素样修饰蛋白（SUMO）化介导的转录后修饰参与包括人类精子发生在内的众多细胞过程。对于人类雄性减数分裂，我们之前发现小泛素相关修饰因子1（SUMO-1）蛋白在粗线期早期精母细胞中定位于染色质轴，然后随着减数分裂的进行定位于动粒。在此，我们根据SUMO-1和SUMO-2/3的亚细胞定位来描述其可能的功能作用。
对两名正常成年有生育能力男性的睾丸中分离出的蛋白质进行蛋白质免疫印迹和免疫沉淀分析。对4名因辅助生殖技术而接受睾丸精子提取的患者在睾丸活检期间获得的雄性减数分裂细胞进行组合免疫荧光和染色体特异性荧光原位杂交分析。
在粗线期亚阶段，联会复合体（SC）以及SC蛋白（SCP）-1和SCP2可被SUMO-1 SUMO化，但SCP3不能。同样，SUMO-1有两种不同的定位模式：一种与常染色体SC共定位的线性模式，以及在9号和1号染色体着丝粒异染色质附近分离的SUMO-1。与正常组织中粗线期之前无法检测到的SUMO-1不同，SUMO-2/3早在细线期和偶线期就已被识别，并且在一些（但不是全部）粗线期细胞中也有；未检测到线性模式。与SUMO-1类似，SUMO-2/3定位于两种主要的核内亚模式：在人类9号染色体着丝粒附近的单个密集信号，以及与常染色体着丝粒共定位的小的单个灶状信号。
我们的数据表明SUMO-1可能参与常染色体SC的维持和/或保护。SUMO-2/3虽然表达类似，但在男性粗线期可能分别独立发挥作用。
