Abstract：
The Myb proto-oncogene encodes the transcription factor c-MYB, which is critical for hematopoiesis. Distant enhancers of Myb form a hub of interactions with the Myb promoter. We identified a long non-coding RNA (Myrlin) originating from the -81-kb murine Myb enhancer. Myrlin and Myb are coordinately regulated during erythroid differentiation. Myrlin TSS deletion using CRISPR-Cas9 reduced Myrlin and Myb expression and LDB1 complex occupancy at the Myb enhancers, compromising enhancer contacts and reducing RNA Pol II occupancy in the locus. In contrast, CRISPRi silencing of Myrlin left LDB1 and the Myb enhancer hub unperturbed, although Myrlin and Myb expressions were downregulated, decoupling transcription and chromatin looping. Myrlin interacts with the KMT2A/MLL1 complex. Myrlin CRISPRi compromised KMT2A occupancy in the Myb locus, decreasing CDK9 and RNA Pol II binding and resulting in Pol II pausing in the Myb first exon/intron. Thus, Myrlin directly participates in activating Myb transcription by recruiting KMT2A.
摘要：
Myb原癌基因编码转录因子c-MYB，这对造血至关重要。Myb的远处增强子形成与Myb启动子相互作用的中心。我们鉴定了源自-81-kb鼠Myb增强子的长非编码RNA(Myrlin)。Myrlin和Myb在红系分化过程中协调调节。使用CRISPR-Cas9的MyrlinTSS缺失减少了Myb增强子上的Myrlin和Myb表达以及LDB1复合物占用，损害增强子接触并减少基因座中的RNAPolII占据。相比之下,Myrlin的CRISPRi沉默使LDB1和Myb增强子集线器不受干扰，尽管Myrlin和Myb表达下调，解耦转录和染色质循环。Myrlin与KMT2A/MLL1复合物相互作用。MyrlinCRISPRi损害了Myb基因座中KMT2A的占有率，降低CDK9和RNAPolII结合并导致PolII在Myb第一外显子/内含子中暂停。因此，Myrlin通过募集KMT2A直接参与激活Myb转录。
