Complex formation by the Drosophila MSL proteins: role of the MSL2 RING finger in protein complex assembly

Abstract

Drosophila MSL proteins are thought to act within a complex to elevate transcription from the male X chromosome. We found that the MSL1, MSL2 and MSL3 proteins are associated in immunoprecipitations, chromatographic steps and in the yeast two-hybrid system, but that the MLE protein is not tightly complexed in these assays. We focused our analysis on the MSL2-MSL1 interaction, which is postulated to play a critical role in MSL complex association with the X chromosome. Using a modified two-hybrid assay, we isolated missense mutations in MSL2 that disrupt its interaction with MSL1. Eleven out of 12 mutated residues clustered around the first zinc-binding site of the RING finger domain were conserved in a Drosophila virilis MSL2 homolog. Two pre-existing msl2 alleles, which fail to support male viability in vivo, have lesions in the same region of the RING finger. We tested these in the two-hybrid system and found that they are also defective in interaction with MSL1. Mutation of the second zinc-binding site had little effect on MSL1 binding, suggesting that this portion of the RING finger may have a distinct function. Our data support a model in which MSL2-MSL1 interaction nucleates assembly of an MSL complex, with which MLE is weakly or transiently associated.

Coregulator Small Nuclear RING Finger Protein (SNURF) Enhances Sp1- and Steroid Receptor-mediated Transcription by Different Mechanisms

“…The C-terminal region of SNURF harbors a consensus sequence for a C 3 HC 4 -type zinc finger, the so-called RING finger, which is present in several transcriptional regulatory proteins and has been proposed to participate in protein-protein interactions (55). Interestingly, the RING finger region of MSL2 protein has been shown to possess multiple interaction surfaces, as mutations in the coordination sites for the first (CS1) and the second zinc (CS2) atoms have distinct effects on its interactions and functions (56). Our results suggest that similar to MSL2, the RING finger region of SNURF may not act as a single functional unit, as mutations in the first and the second zinc coordination sites had dissimilar consequences in COS-1 and CV-1 cells.…”

Ci antagonizes Hippo signaling in the somatic cells of the ovary to drive germline stem cell differentiation

“…First, Vg could form a complex with Sd in S2 cells ( Figure 2H) [21,22]. Here, we want to note that although they are male cells [34,35], S2 cells have been widely used in Drosophila biochemical studies. Cell culture system sometimes may not recapitulate what is happening in vivo; however, results from cultured cells could provide biochemical hints for mechanistic studies.…”

Structural and Biochemical Studies on the Chromo-barrel Domain of Male Specific Lethal 3 (MSL3) Reveal a Binding Preference for Mono- or Dimethyllysine 20 on Histone H4

“…The precise targeting and substrate specificity of MOF relies on the presence of components distinct from the catalytic subunit (3,4,7,8). Specifically, in the MOFcontaining Drosophila male specific lethal (MSL) complex, the MSL3 protein is required for chromatin targeting, nucleosome binding, histone tail substrate recognition, and maximal MOF HAT activity (16 -20).The most well studied MOF-containing complex is the Drosophila melanogaster male specific lethal or MSL complex that binds selectively to large regions of the X-chromosome in male flies (14,15,(21)(22)(23)(24)(25)(26) where it is enriched at the 3Ј ends of actively transcribed genes (27-30) and acetylates lysine 16 on histone H4 (H4K16Ac) (22, 31), thereby balancing male Xchromosomal gene expression. The Drosophila MSL complex contains the dMSL1, dMSL2, and dMSL3 proteins, the RNA/ DNA helicase MLE, the HAT enzyme MOF, and one of two apparently functionally redundant non-coding RNAs (roX1 and roX2) (reviewed in Refs.…”

“…14, 15, and 21). The absence of any of the MSL components results in male lethality (14,15,(23)(24)(25)(26)). The precise specificity of MOF for H4K16 and the targeting to specific domains of the male X-chromosome is determined by other components of the complex, in particular 23,26,[28][29][30]32).…”