Many proteins achieve their function by acting as part of multiprotein complexes. The formation of these complexes is highly regulated and mediated through domains of protein–protein interaction. Disruption of a complex or of the ability of the proteins to form homodimers, heterodimers or multimers can have severe consequences for cellular function. In this context, the formation of dimers and multimers can be perturbed by proteins referred to here as ‘micro-Proteins’(miPs), these  are short, usually single-domain proteins that, in analogy to miRNAs, heterodimerize with their targets and exert a dominant-negative effect. These disruptive protein species contain the protein-interaction domains of bona fide interaction partners, but lack the functional domains required for the activation of, for example, transcription or DNA binding. MicroProteins thus behave as post-translational regulators by forming homotypic dimers with their targets, and act through the dominant–negative suppression of protein complex function2 .

                 Photoperiod‐dependent flowering in rice is regulated by HEADING DATE 1 (Hd1), which acts as both an activator and repressor of flowering in a daylength‐ dependent manner. An investigation was carried out to use the  micro-Proteins as a tool to modify rice sensitivity to the photoperiod  by designing a synthetic Hd1 microProtein (Hd1miP) capable of interacting with Hd1 protein and overexpressed it in rice. Transgenic OX‐Hd1miP plants flowered significantly earlier than wild type plants when grown in non‐inductive long day conditions, these results show the potential of micro-Proteins to serve as powerful tools for modulating crop traits and unraveling protein function4.

 

                     Using the synthetic microProtein approach an  investigation was carried out that micro-Proteins are able to regulate multidomain proteins of different classes. It has shown that the multidomain proteins DCL1, BRI1, and CRY1 can be regulated by over-expressing their protein-protein interaction domains as synthetic microProteins. As a result, microProteins can inhibit any multidomain protein containing a protein-protein interaction domain that is part of a higher-order protein complex. The positive regulatory effect of miP-DCL1 on miRNA biogenesis revealed that synthetic microProteins can be used to unravel the biological activity of certain domains. Furthermore, the synthetic microProtein approach can be used as a tool to modify gene functions at the protein level1.

 

     References:  

1.      DOLDE, U., RODRIGUES, V., STRAUB, D., BHATI, K.K., CHOI, S., YANG, S.W., AND WENKEL, S. 2018,Synthetic MicroProteins: versatile tools for post-translational regulation of target proteins. Plant Physiol. 176, 3136–3145.

2.       EGUEN, T., STRAUB, D., GRAEFF, M., AND WENKEL, S. 2015, MicroProteins: small size-big impact. Trends Plant Sci. 20:477–482.

3.      STAUDT, A.C. AND WENKEL, S. 2011, Regulation of protein function by ‘microProteins’. EMBO Rep. 12, 35–42

4.      EGUEN, T., J. G. ARIZA, V. BRAMBILLA, B. SUN, K. K. BHATI et al., 2020, Control of flowering in rice through synthetic microProteins. J. Integr. Plant Biol. 62: 730–736.