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Regulating the expression of individual miRNAs (microRNAs) is important for cell development and function. The up- or down-regulation of the processing of specific miRNA precursors to the mature active form represents one tool to control miRNA concentration and is mediated by proteins that recognize the terminal loop of the RNA precursors. Terminal loop recognition is achieved by the combined action of several RNA-binding domains. The proteins can then regulate the processing by recruiting RNA enzymes, changing the RNA structure and preventing or enhancing the accessibility and processing activity of the core processing complexes. The present review focuses on how terminal loop-binding proteins recognize their RNA targets and mediate their regulatory function(s), and highlights how terminal loop-mediated regulation relates to the broader regulation of mRNA metabolism.

RNA granules have been observed in different organisms, cell types and under different conditions, and their formation is crucial for the mRNA life cycle. However, very little is known about the molecular mechanisms governing their assembly and disassembly. The aggregation-prone LSCRs (low-sequence-complexity regions), and in particular, the polyQ/N-rich regions, have been extensively studied under pathological conditions due to their role in neurodegenerative diseases. In the present review, we discuss recent in vitro, in vivo and computational data that, globally, suggest a role for polyQ/N regions in RNA granule assembly.