Hypoxia activated long non-coding RNA HABON regulates the growth and proliferation of hepatocarcinoma cells by binding to and antagonizing HIF-1 alpha

The adaptation of tumour cells to hypoxic microenvironment is one of the most significant characteristics of many malignant tumour diseases including hepatocarcinoma. Recently, long non-coding RNAs (lncRNAs) have been reported to play important roles in the various levels of gene regulation thus functioning in growth and survival of tumour cells. Here, new hypoxia-related lncRNAs in hepatocarcinoma cells were screened and validated by lncRNA chip-array as well as real-time RT-PCR. Among them, a hypoxia-activated lncRNA that we identified and termed Hypoxia-Activated BNIP3 Overlapping Non-coding RNA (HABON), was not only regulated by hypoxic-induced factor-1α (HIF-1α) but its expression increased significantly under hypoxia in tumour cells. We deciphered the biological characteristics of HABON including its cell localization, genomic location, as well as its full-length sequence, and proved HABON could promote growth, proliferation and clone-formation of hepatocarcinoma cells under hypoxia. Then, we revealed that HABON was transcriptionally activated by HIF-1α in hypoxic cells, furthermore, it could interact with HIF-1α and promote its protein degradation, thus affecting transcription of HIF-1α’s target genes to exert its effects on cells. Besides, the elevated expression of HABON under hypoxia could promote the transcriptional activation of BNIP3 through HIF-1α, and increasing the expression level of BNIP3. This research provides a novel clue for the adaptive survival and growth mechanism of tumour under hypoxia, and gives a way to reveal the nature of tumour cells’ resistance characteristics to harsh microenvironment.肿瘤细胞对缺氧微环境的适应性是包括肝细胞癌在内的多种恶性肿瘤疾病最显著的特征之一。近年来，已有研究表明长链非编码RNA（long non-coding RNAs，lncRNAs）可在多个层面参与基因调控，进而在肿瘤细胞的生长与存活过程中发挥重要作用。本研究通过lncRNA芯片阵列及实时RT-PCR，筛选并验证了肝癌细胞中新型缺氧相关lncRNAs。其中，我们鉴定出一种缺氧激活型长链非编码RNA，并将其命名为缺氧激活BNIP3重叠非编码RNA（Hypoxia-Activated BNIP3 Overlapping Non-coding RNA，HABON）：该RNA不仅受缺氧诱导因子-1α（hypoxia-inducible factor-1α，HIF-1α）调控，且在肿瘤细胞缺氧条件下其表达水平显著升高。我们解析了HABON的生物学特性，包括其细胞定位、基因组位置及全长序列，并证实其可在缺氧条件下促进肝癌细胞的生长、增殖与克隆形成。随后研究发现，HABON可在缺氧细胞中被HIF-1α转录激活；进一步研究表明，HABON可与HIF-1α相互作用并促进其蛋白质降解，进而通过调控HIF-1α靶基因的转录发挥细胞生物学功能。此外，缺氧条件下HABON表达升高可通过HIF-1α促进BNIP3的转录激活，提升BNIP3的表达水平。本研究为肿瘤在缺氧微环境中的适应性存活与生长机制提供了全新的研究线索，也为揭示肿瘤细胞对恶劣微环境的抵抗特性的本质提供了新的思路。