Dissection of Genetic Pathways in C. elegans - Caenorhabditis Elegans: Molecular Genetics and Development - page 120

Fig. 2 Possible genetic scenarios where the phenotype of a hypormorphic allele can be enhanced. A hypomorphic mutation
(X) causes partial loss of gene function, which only slightly reduces the activity of a corresponding signaling pathway. This
reduction can be dramatically enhanced by loss or reduction in the activity of a gene (Y) that encodes a physical interacting
partner (i), acts upstream (ii), downstream (iii) of the same pathway, or functions in a parallel pathway that functionally
compensate for each other (iv). (For color version of this figure, the reader is referred to the web version of this topic.)

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1995 ). EOR-1, a putative transcription factor related to the human oncogene PLZF ( Hoeppner et al., 2004 ), and EOR-2, a novel
protein ( Hoeppner et al., 2004 ), act downstream or in parallel to MPK-1 and function redundantly with LIN-1 to regulate
transcription of target genes ( Howell et al., 2010; Rocheleau et al., 2002 ). LET-23 signaling is also regulated by several negative
regulators, include ARK-1 (Ack) ( Hopper et al., 2000 ), SLI-1 (c-Cbl), which targets activated LET-23 for internalization and
degradation ( Rubin et al., 2005; Swaminathan and Tsygankov, 2006 ), UNC-101 and APM-1, which encode medium chains of
the AP-1 adaptin and promote LET-23 endocytotic recycling ( Lee et al., 1994; Shim et al., 2000 ), and GAP-1, which stimulates
LET-60 GTP hydrolysis ( Hajnal et al., 1997 ). More details about this pathway can be found elsewhere ( Sundaram, 2006 ). The
mammalian homologs of these genes are indicated in parentheses. (For color version of this figure, the reader is referred to the
web version of this topic.)