Mechanism of sex steroid hormones in gene expression control through line-1

Abstract

Long interspersed elements-1s (LINE-1s or L1s) was shown to play an important role in gene regulation. We further investigated the role of LINE-1s in gene regulation when the genes are under influence of hormones. The regulated mRNA levels of genes containing LINE-1 from the sex hormones treated experiments (available from Gene Expression Omnibus (GEO) (http://www.ncbi.nlm.nih.gov/geo)), gene expression database, was compared by chi-square. From the analyzed results, three types of sex hormones are strongly associated with expression of genes containing LINE-1. Firstly, in particular, 100 nM estradiol (E2) was associated with up-regulated genes containing LINE-1 at 3, 6 and 12 incubating hours, respectively (p-value = 6.38E-07, OR (95%CI) 1.43(1.24-1.64); p-value =4.50E-13, OR(95%CI) 1.59(1.40-1.81) and p-value =1.18E-15, OR(95%CI) 1.64(1.45-1.85)). For progesterone, we found that 10 nM of PG at 16 hours was related to down-regulated genes containing LINE-1 (p-value =9.53E-06, OR (95%CI) 1.65(1.32-2.06)). Lastly, the 10 nM of dihydrotestosterone (DHT) was shown to be associated with lower expression of genes containing LINE-1 (p-value =3.81E-14, OR (95%CI) 2.01(1.67-2.42)). The similar results in vitro and from database analysis were shown in 100 nM E2 which can induce the increasing of LINE-1s and also in genes containing LINE-1 expression after 12 hours for incubating time in breast cancer cells (MCF-7 cell lines). In contrast for PG, LINE-1s expression in breast cancer cells (T-47D cell lines) were not shown to have stable trends as expected. However, the influence of E2 to the expression of gene containing LINE-1 was supported by estrogen antagonist (Tamoxifen) experiment. Lower expression in both LINE-1s and genes containing LINE-1 was found after treating samples with Tamoxifen. On the other hand, the number of up-regulated probes were found higher at after LINE-1 position. Whole RNA sequencing using Hiseq 2000 was used to confirm the increasing of LINE-1 isoform which are produced by LINE-1 transcription in the E2 treated cells. Moreover, the role of ERE in E2 inducing genes pathway was analyzed by overlapping the genes which are up-regulated in E2 experiments with genes containing LINE-1. The results showed that ERE might not play a major role in E2 inducing transcription in genes containing LINE-1. Then, analyzing data from microarray expression was shown the association of estrogen early immediate genes (c-fos) which was related in the increasing of gene containing LINE-1 expression process. Chromatin immunoprecipitation (ChIP) was used to demonstrate this association and ChIP results showed the binding site of this transcription factors at 5’ LINE-1 promoter. The relate function of c-fos was found at 12 hours for binding time at LINE-1 promoter. These findings indicate the new route of sex hormones in using LINE-1 to control gene expression.