Reviewer #3 (Public Review):
The manuscript by Jera and coworkers describes an internal long-range interaction within the dynein intermediate chain, which can be relieved by light chain binding to provide access for additional protein ligands, and partly by binding of specific protein ligands. The work uses a suite of biophysical methods including AUC, SEC-MALS, and NMR spectroscopy, and a palette of protein constructs and complexes to assess complex sizes and stoichiometries, pinpointing by NMR the molecular details. The molecular auto-inhibition is supported by the data and is likely to be of general interest. The strength of the manuscript is the use of full-length proteins/longer regions and thus the investigation of higher-order complexes within context, which have been crucial to elucidate an important and likely biologically relevant autoinhibitory state in dynein as well as its modulation.
The manuscript by Jera et al is in general very well written, the experiments have been thoroughly conducted and analyzed, and the conclusions are generally well supported by data. The work delivers important new insight into a case where disordered linkers may enable molecular functions. However, the significance of the finding for the biological function of dynein is not clear. How is it anticipated that the observed differential autoinhibition of dynein will affect the biological outcomes?
Below are some recommendations that I find may improve the manuscript.
As a non-dynein expert, I found the introduction into the protein system to be too superficial and the model shown in Fig. 1B, did not help much (e.g. the light chains were hard to acknowledge as they appear to be rather small compared to the IC chain and was at first overlooked at just the binding sites; where is the heavy chain of dynein, why is there no coiled coil of p150, etc?). The biological role of dynein is not explained particularly well in the introduction and the biological relevance of the findings is too briefly addressed. I suggest a much more detailed description of the system at the beginning of the introduction including the biological relevance of the different ligands, which should include an upgrade of figure 1b, with more detail on domains, etc. Also, the abstract would benefit from a more precise description of the biological question and why this study is relevant, and the title is also very broad. Finally, how autoinhibition plays a role in the biological function of dynein should be more clearly discussed in the discussion, e.g., what is the relevance of the differential binding of the two ligands and their differential effects on the autoinhibited state. Which biological outcomes are to be expected?
One of the conclusions is that the internal contacts occur between the C-terminal of the IC and SAH/H2, which is seen from the intensity changes in the HSQC spectra upon addition of the 160-240 construct to the 1-88 construct. However, adding the linker part from 100-160 produces a much more pronounced effect (Fig. 5C, bottom), suggesting that residues in this region, which includes the Tctex and LC8 binding motifs play additional roles. Is the binding of the light chains to IC of higher affinity to the 100-160 protein than to the 1-260? In that case, this could suggest that also inhibitory access to these two sites occurs in the autoinhibited state. The additional effect of the 100-160 residues should be addressed.
Can H3 be excluded as a player in the internal interactions, just because you see binding to the LC7 site when studied in isolation? Once the LC7 regions is bound, H3 may also participate, as also clearly indicated from the data shown in Fig. 4A. Using an H3 peptide would be relevant.
Fig6B and associated text: there is a clear although weak loss in intensity/peak volume in the H2 region for the interaction with NudE. Why assume that there is no interaction? The affinity for NudE is lower, so the concentration of the complex will also be lower at similar conditions compared to that of p150, and this would give rise to the smaller effects in the spectra. In the lower panel, there is a clear indication of binding to H2 as well, and SAH and H2 binding may very well be cooperative as they are sequentially close. What are the relative concentrations of NudE and p150 in the cell? Would they be competitive despite the difference in affinities? Can a mechanism for p150 ability to relieve autoinhibition be proposed - from Fig6B, could it be able to bind first to the H2 region even though SAH is involved in the autoinhibitory interaction?