STRING 9.05 
SMAD4 [ENSP00000341551]
 
SMAD family member 4; Common mediator of signal transduction by TGF-beta (transforming growth factor) superfamily; SMAD4 is the common SMAD (co-SMAD). Promotes binding of the SMAD2/SMAD4/FAST-1 complex to DNA and provides an activation function required for SMAD1 or SMAD2 to stimulate transcription. May act as a tumor suppressor
SMAD1 [ENSP00000305769]
 
SMAD family member 1; Transcriptional modulator activated by BMP (bone morphogenetic proteins) type 1 receptor kinase. SMAD1 is a receptor-regulated SMAD (R-SMAD)
Evidence suggesting a functional link:
Neighborhood in the Genome:  
none / insignificant.
    
Gene Fusions:  
none / insignificant.
    
Cooccurence Across Genomes:  
none / insignificant.
    
Co-Expression:  
none / insignificant.
    
Experimental/Biochemical Data:   yes (score 0.999). In addition, putative homologs were found interacting in other species (score 0.136).  
Association in Curated Databases:   yes (score 0.800).  
Co-Mentioned in PubMed Abstracts:   yes (score 0.569). In addition, putative homologs are mentioned together in other species (score 0.085).  
Combined Score:
 
0.999
 
Note: the two proteins have some sequence similarity (330.7 bits over 440 amino acids. click here to see the alignment).
Evidence for specific actions:
Binding:yes (score: 0.998)