新出现的证据表明，超出注释的翻译组的神秘翻译会产生具有发育或生理功能的蛋白质。然而，神秘的非规范开放阅读框（ORF）在癌症中的功能仍然很大程度上未知。为了填补这一空白并系统地识别结直肠癌 (CRC) 对非规范 ORF 的依赖，我们应用了综合多组学策略，将核糖体分析和 CRISPR-Cas9 敲除筛选与大规模分子和临床数据分析相结合。与正常组织相比，许多此类 ORF 在 CRC 中表达上调，并且与临床相关分子亚型相关。我们证实了微蛋白 SMIMP 的体内促肿瘤功能，该功能由灵长类特异性长非编码 RNA 编码，其表达与结直肠癌的不良预后相关，在正常组织中表达量较低，在结直肠癌和一些结直肠癌中表达量特别升高。其他癌症类型。从机制上讲，SMIMP 与 SMC1A（黏连蛋白复合物的核心亚基）的 ATP 酶形成域相互作用，并促进 SMC1A 与顺式调控元件结合，从而促进对 CDKN1A 和 CDKN2B 编码的肿瘤抑制细胞周期调节因子的表观遗传抑制。因此，我们的研究揭示了一种神秘的微生物蛋白是粘连蛋白介导的基因调控的重要组成部分，并表明由神秘的非规范 ORF 编码的“暗”蛋白质组可能包含潜在的治疗或诊断靶标。© 2023。 ）。

Emerging evidence suggests that cryptic translation beyond the annotated translatome produces proteins with developmental or physiological functions. However, functions of cryptic non-canonical open reading frames (ORFs) in cancer remain largely unknown. To fill this gap and systematically identify colorectal cancer (CRC) dependency on non-canonical ORFs, we apply an integrative multiomic strategy, combining ribosome profiling and a CRISPR-Cas9 knockout screen with large-scale analysis of molecular and clinical data. Many such ORFs are upregulated in CRC compared to normal tissues and are associated with clinically relevant molecular subtypes. We confirm the in vivo tumor-promoting function of the microprotein SMIMP, encoded by a primate-specific, long noncoding RNA, the expression of which is associated with poor prognosis in CRC, is low in normal tissues and is specifically elevated in CRC and several other cancer types. Mechanistically, SMIMP interacts with the ATPase-forming domains of SMC1A, the core subunit of the cohesin complex, and facilitates SMC1A binding to cis-regulatory elements to promote epigenetic repression of the tumor-suppressive cell cycle regulators encoded by CDKN1A and CDKN2B. Thus, our study reveals a cryptic microprotein as an important component of cohesin-mediated gene regulation and suggests that the 'dark' proteome, encoded by cryptic non-canonical ORFs, may contain potential therapeutic or diagnostic targets.© 2023. The Author(s).